Cathode active material, cathode, and nonaqueous electrolyte battery

ABSTRACT

A cathode active material has: a lithium composite oxide which contains the highest proportion of nickel among constituent metal elements except lithium; and a phosphorus compound which is contained near the surface of the lithium composite oxide, and a cathode including the cathode active material.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 12/059,939 filed on Mar. 31, 2008, which claims priority to JapanesePatent Application No. 2007-093381 filed on Mar. 30, 2007, and JapanesePatent Application No. 2007-259336 filed on Oct. 3, 2007, the entirecontents of which are being incorporated herein by reference.

BACKGROUND

The present application relates to a cathode active material, a cathode,a nonaqueous electrolyte battery, and a method for manufacturing acathode. More specifically, it relates to a cathode active materialcontaining a lithium composite oxide, a cathode, a nonaqueouselectrolyte battery, and a method for manufacturing a cathode fornonaqueous electrolytic solution secondary batteries.

In recent years, a portable equipment, such as a video camera and anotebook computer is widely used, and there is a strong demand for asecondary battery having a small size and a high capacity. An example ofthe secondary battery currently in use is a nickel-cadmium batteryformed by using an alkali electrolytic solution. The battery voltage isas low as about 1.2 V, and thus it is difficult to improve the energydensity. Therefore, a lithium metal secondary battery using lithiummetal having a specific gravity of 0.534 which is the lightest among thesimple substances of solids, an extremely base potential, and thehighest current capacity per unit mass among metal anode materials hasbeen developed.

However, as for the secondary battery formed using lithium metal as ananode, when the lithium metal secondary battery is charged anddischarged, lithium is grown into a dendrite form in the anode, whichcause problems such as the deterioration in the cycle characteristics ofthe secondary battery and the occurrence of an internal short circuitdue to lithium penetrating through a separator that is arranged so thatthe cathode is not contact with the anode.

Then, for example, as disclosed in Japanese Patent Application Laid-Open(JP-A) No. 62-90863, a secondary battery in which a carbonaceousmaterial such as coke is used for an anode, and charge and dischargecycles are repeated by doping or de-doping an alkali metal ion has beenproposed. Thus, it is found that the defect of the deterioration of theanode caused by repeating charge and discharge cycles can be avoided byusing the secondary battery.

On the other hand, as a cathode active material capable of obtaining abattery voltage of approximately 4 V, inorganic compounds such astransition metal oxides including alkali metal and transition metalchalcogens are known. Among them, a lithium composite oxide such aslithium cobalt oxide or lithium nickel oxide holds great promise interms of a high potential, stability and long life.

Among them, a high-nickel cathode active material typified by Li_(x)NiO₂is a lithium composite oxide which contains the highest proportion ofnickel Ni among constituent metal elements except lithium. The cathodeactive material shows a higher discharging capacity as compared toLi_(x)CoO₂ and is an attractive cathode material.

However, larger amounts of LiOH which is a residue of a cathode rawmaterial (an impurity) as well as Li₂CO₃ which is produced by carbondioxide gas absorption by LiOH in the air are present on the surface ofthe high-nickel cathode active material as compared to that ofLi_(x)CoO₂.

Since LiOH in the impurities is an alkali component, when the cathodeactive material is kneaded with polyvinylidene fluoride (PVdF) to beused as a binder and N-methyl-2-pyrrolidone (NMP) in a step offabricating a cathode, or when the solvent is applied after thekneading, the gelation of the solvent is caused.

Li₂CO₃ in the impurities is hardly dissolved in the solvent or theelectrolytic solution, however, it is decomposed by the charging anddischarging operation, thereby generating gases CO₂ and CO₃. These gascomponents increase the pressure inside the battery and lead to theexpansion of the battery as well as the deterioration of cycle life. Inthe case where an exterior member of the battery is made of a stainlesssteel (SUS) can or an aluminum can and has a high strength, the batterycan be damaged by the increased internal pressure due to the generationof gas.

As a method for preventing the gelation, there is a method forneutralizing the alkali component so as to be Li₂CO₃ by once storing thehigh-nickel cathode active material in carbon dioxide gas. However, thepH of the cathode active material after the neutralization is higherthan that of Li_(x)CoO₂. Therefore, the decomposition of theelectrolytic solution is facilitated and gases CO₂ and CO₃ aregenerated.

Thus, as another method for preventing the gelation, a method forpreventing the gelation as well as inhibiting the generation of gas isdisclosed in JP-A No. 2006-286240. In this method, the residual LiOH isfixed as LiF by treating the cathode active material with a fluorinegas. Therefore, the gelation can be prevented and the generation of gascan be inhibited.

In addition to the above-described problems, there are further problemsthat the volume density of the electrode is low due to the compositionand shape of the high-nickel cathode active material and the windingcharacteristics of an electrode are poor.

In order to compare a typical shape of Li_(x)CoO₂ with a shape ofLi_(x)NiO₂, electron microscope images of one example of Li_(x)CoO₂ andone example of Li_(x)NiO₂ are shown in FIGS. 1A and 1B. FIG. 1A shows anelectron microscope image of an example of Li_(x)CoO₂. FIG. 1B shows anelectron microscope image of an example of LixNO₂. In the high-nickelcathode active material, a true specific gravity of the powder is loweras compared to that of Li_(x)CoO₂, and thus it may be impossible toimprove the reduction in the volume density of the electrode by thecomposition.

Further, a battery with a cylindrical shape can be produced by using thehigh-nickel cathode active material. In the case where a battery with aflat type, used for portable telephones, is produced, a curve is tightat the time of folding the electrode because the winding characteristicsof an electrode are poor. Furthermore, the electrode may be broken orcut at the time of folding the electrode by winding or at the time ofmolding by pressing after the winding, and therefore it is difficult toproduce the battery with a flat type.

In related art, a method for improving the strength by increasing thethickness of electrode foil-shaped or a method for reducing the volumedensity of the cathode active material applied to the electrode foil hasbeen proposed as a method for reducing the cracking and cutting of theelectrode by winding and pressing.

The method of fluorination treatment proposed in JP-A No. 2006-286240has the following problems (1) to (3):

(1) fluorine gas is highly toxic and difficult to handle;

(2) the internal resistance of the battery is increased by LiF producedas a by-product material and thus the capacity is decreased, and furtherthe capacity is decreased by the corrosion due to the fluorine gas inthe cathode active material; and further (3) the residual F is easilyreacted with minute amounts of moisture present in the active materialand the electrolytic solution to generate HF, thereby causing the cycledeterioration.

With reference to the problems of the volume density of the electrodeand the winding characteristics of the electrode, when theabove-described method in related art is used, the amount of the cathodeactive material relative to the volume of the battery is reduced. As aresult, it may be impossible to obtain a sufficient capacity. Further,even if it can be wound, it is difficult to mold by pressing. Thebattery at a laboratory level can be fabricated by using a method forwinding while the electrolytic solution is applied to the electrode or amethod including the steps of winding, impregnating with theelectrolytic solution, molding, and removing the excessive electrolyticsolution in place of a method for molding by pressing. However, thereare some problems that the composition of the electrolytic solution tobe produced and the amount of the electrolytic solution become unclear.

SUMMARY

Therefore, it is desirable to provide a cathode active material, acathode, and a nonaqueous electrolyte battery in which the gasgeneration can be inhibited by reducing LiOH and Li₂CO₃ which areimpurities in high-nickel cathode active material and thus the cyclecharacteristics can be improved.

Furthermore, there is an another purpose of providing a cathode activematerial, cathode, and nonaqueous electrolyte battery which are capableof improving the winding characteristics of an electrode by changing thedistribution of binders and conductive auxiliary agents in theelectrode.

However, when the method for improving the strength by increasing thethickness of electrode foil-shaped or the method for reducing the volumedensity of the cathode active material applied to the electrode foil isused, the amount of the cathode active material relative to the volumeof the battery is reduced. As a result, it may be impossible to obtain asufficient capacity. Further, even if it can be wound, it is difficultto mold by pressing. The battery at a laboratory level can be fabricatedby using a method for winding while the electrolytic solution is appliedto the electrode or a method including the steps of winding,impregnating with the electrolytic solution, molding, and removing theexcessive electrolytic solution in place of a method for molding bypressing. However, there are some problems that the composition of theelectrolytic solution to be produced and the amount of the electrolyticsolution become unclear.

Further, when Li_(x)CoO₂ is used, it is necessary to apply Li_(x)CoO₂thickly and densely for improving the capacity of the battery andincreasing the amount of the cathode active material included in thebattery. However, it is difficult to resist the winding curve of theflat type battery when a thick and high-density electrode is used.

Therefore, there is a purpose of providing a method for manufacturing acathode capable of improving the winding characteristics of an electrodeby changing the distribution of binders and conductive auxiliary agentsin the cathode.

In order to solve the above problems, according to an embodiment, thereis provided a cathode active material including a lithium compositeoxide which contains the highest proportion of nickel is contained amongconstituent metal elements except lithium and a phosphorus compound nearthe surface of the lithium composite oxide.

According to an embodiment, there is provided a cathode including thecathode active material having a lithium composite oxide which containsthe highest proportion of nickel among constituent metal elements exceptlithium; and a phosphorus compound which is contained near the surfaceof the lithium composite oxide.

According to an embodiment, there is provided a nonaqueous electrolytebattery including a cathode, an anode, and an electrolyte, where thecathode has the cathode active material having a lithium composite oxidewhich contains the highest proportion of nickel is contained amongconstituent metal elements except lithium and a phosphorus compound nearthe surface of the lithium composite oxide.

According to an embodiment, there is provided a method for manufacturinga cathode including the steps of: mixing phosphorous acid (H₃PO₃) withcathode active material to prepare a cathode mixture slurry; andapplying the cathode mixture slurry to a cathode current collector toform a cathode active material layer.

In an embodiment, LiOH, which is a impurity, is converted to phosphoricacid lithium with a low reactivity by treating with phosphorous acid orphosphoric acid compound and thus the amount of LiOH and Li₂CO₃ producedby reaction with LiOH are reduced. Therefore, the absorption of carbondioxide gas in the air, the generation of gas, and the deterioration ofcycle characteristics can be inhibited.

In an embodiment, the winding characteristics of an electrode isimproved by changing the distribution of binders and conductiveauxiliary agents in the electrode.

In an embodiment, the distribution of binders and conductive auxiliaryagents in the cathode active material layer is changed by mixing thecathode active material with phosphorous acid (H₃PO₃) when preparing thecathode mixture slurry, which allows for improving the windingcharacteristics of an electrode.

According to an embodiment, the gas generation can be inhibited and thusthe cycle characteristics can be improved. In addition, the windingcharacteristics of an electrode can be improved.

According to an embodiment, the winding characteristics of a cathode areimproved by changing the distribution of binders and conductiveauxiliary agents in the cathode.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B are electron micrographs of an example of Li_(x)CoO₂ andLi_(x)NiO₂;

FIG. 2 is a perspective view showing a structural example of thenonaqueous electrolyte battery according to a first embodiment;

FIG. 3 is a cross-sectional view along the line II-II of a spiralelectrode body 110 shown in FIG. 2;

FIG. 4 is a cross-sectional view showing a structural example of thenonaqueous electrolyte battery according to a third embodiment;

FIG. 5 is a partly enlarged cross-sectional view showing a spiralelectrode body 130 shown in FIG. 4;

FIG. 6 is a perspective view showing a structural example of thenonaqueous electrolyte battery according to a fourth embodiment;

FIGS. 7A and 7B are graphs showing load characteristics of a laminatedcell formed by using the cathode electrode in Example 13 and Comparison1;

FIGS. 8A and 8B are electron micrographs of the surface of the cathodeelectrode in Example 13 and Comparison 1;

FIGS. 9A and 9B are graphs showing results of the cathode electrode inExample 21 and Comparison 1 which are determined based on TOF-SIMSpositive secondary ion mass spectrometry;

FIGS. 10A and 10B are graphs showing results of the cathode electrode inExample 21 and Comparison 1 which are determined based on TOF-SIMSpositive secondary ion mass spectrometry;

FIG. 11 is graphs showing results of the cathode electrode in Example 21and Comparison 1 which are determined based on TOF-SIMS negativesecondary ion mass spectrometry;

FIG. 12 is a graph showing results of the surface analysis by X-rayphotoelectron spectroscopy in Example 21 and Comparison 1;

FIG. 13 is a perspective view showing a first example of the nonaqueouselectrolyte battery;

FIG. 14 is a cross-sectional view along the line II-II of the spiralelectrode body 110 shown in FIG. 2;

FIG. 15 is a cross-sectional view showing a third example of thenonaqueous electrolyte battery;

FIG. 16 is a partly enlarged cross-sectional view showing the spiralelectrode body 130 shown in FIG. 4;

FIG. 17 is a perspective view showing a fourth example of the nonaqueouselectrolyte battery;

FIGS. 18A and 18B are electron micrographs of the surface of the cathodeelectrode in Samples 2 and 12;

FIGS. 19A and 19B are graphs showing results of the cathode electrode inSamples 2 and 12 which are determined based on TOF-SIMS positivesecondary ion mass spectrometry;

FIGS. 20A and 20B are graphs showing results of the cathode electrode inSamples 2 and 12 which are determined based on TOF-SIMS positivesecondary ion mass spectrometry;

FIG. 21 is graphs showing results of the cathode electrode in Samples 2and 12 which are determined based on TOF-SIMS negative secondary ionmass spectrometry; and

FIG. 22 is a graph showing results of the surface analysis by X-rayphotoelectron spectroscopy in Samples 2 and 12.

DETAILED DESCRIPTION

The present application will be described with reference to theaccompanying drawings according to an embodiment. First, an example ofthe structure of the nonaqueous electrolyte battery according to thefirst embodiment will be described with reference to FIGS. 2 and 3.

FIG. 2 is a perspective view showing a structural example of thenonaqueous electrolyte battery according to the first embodiment. Thenonaqueous electrolyte battery is, for example, a nonaqueous electrolytesecondary battery. The nonaqueous electrolyte battery has the spiralelectrode body 110 on which the cathode lead 111 and the anode lead 112are mounted in a film-shaped exterior member 1 and has a flat type.

Each of the cathode lead 111 and the anode lead 112 has a stripe-shaped,and is drawn, respectively from the inside of the exterior member 101 tothe outside, for example, in the same direction. The cathode lead 111 ismade of metallic materials such as aluminium Al and the anode lead 112is made of metallic materials such as nickel Ni.

The exterior member 101 is a laminated film having a structure in which,for example, the insulating layer, the metal layer, and the outermostare stacked sequentially in this order and then combined by lamination.In the exterior member 101, for example, the insulating layer is facedinwardly and the respective outer edges are bonded by welding or byusing adhesives.

The insulating layer is made of polyethylene, polypropylene, modifiedpolyethylene, modified polypropylene or polyolefin resins such ascopolymers thereof. This is because the moisture permeability isdecreased and an excellent airtightness is provided. The metal layer ismade of aluminium, stainless steel, nickel, or iron in foil-shaped orplate form. The outermost layer may be made of, for example, the sameresin as that of the insulating layer and further may be made of nylon.This is because resistance to breakage or sticking can be improved. Theexterior member 101 may include other layers in addition to theinsulating layer, the metal layer, and the outermost layer.

In order to improve the adhesion of the cathode lead 111 and the anodelead 112 to the inside of the exterior member 101 and prevent outsideair from entering, an adherent film 102 is inserted between the exteriormember 101 and the cathode lead 111, and between the exterior member 101and the anode lead 112. The adherent film 102 is made of a materialhaving adhesion to the cathode lead 111 and the anode lead 112. Forexample, the adherent film is preferably made of polyolefin resins suchas polyethylene, polypropylene, modified polyethylene, or modifiedpolypropylene in the case where the cathode lead 111 and the anode lead112 is made of the metallic materials described above.

FIG. 3 is a cross-sectional view along the line II-II of the spiralelectrode body 110 shown in FIG. 2. The spiral electrode body 110 isformed by stacking a cathode 113 and an anode 114 via a separator 115and an electrolyte 116 and winding them. The outermost periphery thereofis protected by a protective tape 117.

For example, the cathode 113 has a cathode current collector 113A and acathode active material layer 113B that is formed on both sides of thecathode current collector 113A. The cathode current collector 113A ismade of metal foil such as aluminum foil.

The cathode active material layer 113B contains the cathode activematerial having a lithium composite oxide which contains the highestproportion of nickel is contained among constituent metal elementsexcept lithium and a phosphorus compound near the surface of the lithiumcomposite oxide. The cathode active material layer 113B further containsa conductive auxiliary agent such as a carbon material and a binder suchas polyvinylidene fluoride or polytetrafluoroethylene. In the case wherethe highest proportion of nickel among constituent metal elements exceptlithium is contained, the content of constituent metal elements exceptlithium is equivalent to that of nickel. In the case where this contentis highest as compared to the content of constituent metal elementsexcept lithium other than these, the condition falls under theabove-described condition.

Specific examples of the lithium composite oxide, which contains thehighest proportion of nickel among constituent metal elements exceptlithium, include lithium composite oxides having an average compositionrepresented by Formula 1:Li_(x)Co_(y)Ni_(z)M_(1-y-z)O_(b-a)X_(a)  (Chemical formula 1)

wherein M is one or more elements selected from the group consisting ofboron B, magnesium Mg, aluminium Al, silicon Si, phosphorus P, sulfur S,titanium Ti, chromium Cr, manganese Mn, iron Fe, copper Cu, zinc Zn,gallium Ga, germanium Ge, yttrium Y, zirconium Zr, molybdenum Mo, silverAg, barium Ba, tungsten W, indium In, tin Sn, lead Pb, and antimony Sb;X is halogen; and x, y, z, a, and b are values in the range of0.8<x≦1.2, 0≦y≦0.5, 0.5≦z≦1.0, 1.8≦b≦2.2, and 0≦a≦1.0, respectively.

A phosphorus compound is a compound in which the binding energy peak inthe P 2p spectrum based on X-ray photoelectron spectroscopy is in therange of 132 to 135 eV. At least a part of the phosphorus compound is aphosphorus compound represented by, for example, Formula 2 or 3:Li_(c)H_(d)P_(e)O_(f)  (Chemical formula 2)wherein c, e, and f represent an integer of 1 or more; and d representsan integer of 0 or more,Li_(g)PO_(h)F_(i)  (Chemical formula 3)

wherein g, h, and i represent an integer of 1 or more.

These phosphorus compounds are present near the surface of lithiumcomposite oxide particles, for example, it is present so as to cover thelithium compound oxide particles.

As a method for confirming that these phosphorus compounds are presentnear the surface of lithium composite oxide particles, for example, amethod in which the cathode 113 is embedded in resin and then thedistribution in the cross section is determined by Time-of-Flightsecondary Ion Mass Spectrometry (TOF-SIMS) is listed. Alternatively, itcan be confirmed by analyzing elements by X-ray photoelectronspectroscopy while the cathode surface is spattered with argon.

In the case where the cathode active material is analyzed in accordancewith the method shown in JIS-R-9101, the concentrations of carbonate andbicarbonate are preferably 0.3 parts by weight or less. When theconcentrations of bicarbonate and carbonate exceeds 0.3 parts by weight,bicarbonate and carbonate are decomposed by the charging and dischargingoperation and the amount of generated gas is increased, which causesbattery expansion or deterioration in the cycle characteristics.

The cathode active material layer 113B has a peak of a fragment of atleast one secondary ion selected from the group consisting of positivesecondary ions of Li₄PO₄, C₃F₅, C₅F₉, C₇F₁₃, negative secondary ions ofPO₂, PO₃, LiP₂O₄, LiP₂O₅, LiP₂O₆, LiPO₂F, LiPO₃F, POF₂, PO₂F₂, andLiPO₃H based on the surface analysis by TOF-SIMS is observed near thesurface.

The cathode active material layer 113B may be formed in the followingmanner as described in the first and second examples.

In the first example, a cathode active material is kneaded with a bindersuch as polyvinylidene fluoride (PVdF) and a conductive auxiliary agentsuch as graphite to produce a cathode mixture slurry. The cathodemixture slurry is applied to the cathode current collector 113A, whichis dried and the cathode active material layer 113B is formed.

Here, the cathode active material obtained by mixing lithium compositeoxide which contains the highest proportion of nickel among constituentmetal elements except lithium with a compound containing at least eitherPO₃ or PO₄ and then firing is used.

This cathode active material contains the phosphorus compound which iscontained near the surface of the lithium composite oxide. Usableexamples of the lithium composite oxide, which contains the highestproportion of nickel among constituent metal elements except lithium,include lithium composite oxides having the average compositionrepresented by Formula 1.

The phosphorus compound contained near the surface of the lithiumcomposite oxide is, for example, a compound in which the binding energypeak in the P 2p spectrum based on X-ray photoelectron spectroscopy isin the range of 132 to 135 eV. At least a part of the phosphoruscompound is represented by, for example, Formula 2:Li_(c)H_(d)P_(e)O_(f)  (Chemical formula 2)

wherein c, e, and f represent an integer of 1 or more; and d representsan integer of 0 or more.

Further, the cathode active material has a peak of a fragment of atleast one secondary ion selected from the group consisting of a positivesecondary ion of Li₄PO₄, negative secondary ions of PO₂, PO₃, LiP₂O₄,LiP₂O₅, and LiP₂O₆ based on the surface analysis by Time-of-Flightsecondary Ion Mass Spectrometry (TOF-SIMS).

The cathode active material may be formed, for example, in the followingmanner. First, for example, oxide containing nickel as an activematerial precursor or hydroxide, lithium salt, and further a compoundcontaining at least either PO₃ or PO₄ are mixed and fired.

Here, examples of the compound containing at least either PO₃ or PO₄include phosphoric acid compounds such as phosphorous acid (H₃PO₃),phosphoric acid (H₃PO₄), and phosphoric acid lithium (Li₃PO₄). Examplesof the oxide containing nickel include compounds represented by Formula4. Examples of the hydroxide containing nickel include compoundsrepresented by Formula 5:Co_(y)Ni_(z)M_(1-y-z)O_(j-a)X_(a)  (Chemical formula 4)Co_(y)Ni_(z)M_(1-y-z)(OH)_(k-a)X_(a)  (Chemical formula 5)

wherein M is one element selected from the group consisting of boron B,magnesium Mg, aluminium Al, silicon Si, phosphorus P, sulfur S, titaniumTi, chromium Cr, manganese Mn, iron Fe, copper Cu, zinc Zn, gallium Ga,germanium Ge, yttrium Y, zirconium Zr, molybdenum Mo, silver Ag, bariumBa, tungsten W, indium In, tin Sn, lead Pb, and antimony Sb; X ishalogen; and y, z, a, j, and k are values in the range of 0≦y≦0.5,0.5≦z≦1.0, 0.8≦j≦1.2, 2≦k≦4, and 0≦a≦0.5, respectively.

PO₃ and PO₄ groups, which are contained in the above-mentioned compound,are acidic and effective in neutralizing the alkalinity of LiOH which isan impurity component. Further, the amount of Li₂CO₃ to be produced isalso decreased by reducing the LiOH component which is easilycarbonated. Here, the LiOH can be neutralized also by using nitric acidcomponents and sulfuric acid components. However, these components causedamage to the active material due to their strong acidity and thedischarging capacity is decreased, and therefore they are notpreferable.

Examples of the lithium salt include lithium salts represented byFormulae 6 and 7.LiOH—H₂O  (Chemical formula 6)LiNO₃  (Chemical formula 7)

It is preferable to add oxide, hydroxide, and lithium salt so that themolar ratio of lithium Li, cobalt Co, nickel Ni, and M is equivalent tothe ratio represented by Formula 1.0.8≦Li/(Co+Ni+M)≦1.2  (Formula 1)

At least either phosphorous acid (H₃PO₃) or phosphoric acid lithium(Li₃PO₄) is added in an amount of 0.1 parts by weight to 5.0 parts byweight based on the total weight of the mixture of lithium saltrepresented by Formula 6 and the lithium salt represented by Formula 7,which is fired in an air or oxygen atmosphere at 700° C. or higher for 5hours. As described above, a cathode active material to be used in thefirst example is obtained.

The cathode active material to be used in the first example may beproduced by adding phosphorous acid (H₃PO₃) to lithium composite oxidewhich contains the highest proportion of nickel among constituent metalelements except lithium and refiring. Similarly, an effect that reducesLiOH and Li₂CO₃, which are impure components is recognized. It ispreferable that the addition amount of phosphorous acid (H₃PO₃) at thattime is in the range shown in Formula 2. It is preferable that therefiring atmosphere is in an oxygen atmosphere.0.2 parts by weight≦addition amount of H₃PO₃≦20 parts byweight  (Formula 2)

In the second example, the lithium composite oxide which contains thehighest proportion of nickel among constituent metal elements exceptlithium is kneaded with a binder such as polyvinylidene fluoride (PVdF)and a solvent such as N-methyl-2-pyrrolidone (NMP), a compoundcontaining at least either PO₃ or PO₄ is further added to produce acathode mixture slurry. The cathode mixture slurry is applied to thecathode current collector 113A, which is dried and the cathode activematerial layer 113B is formed. As described above, conductive auxiliaryagents such as graphites may be added at the time of kneading.

Thus, LiOH (i.e., impurity) can be neutralized by adding the compoundcontaining at least either PO₃ or PO₄ at the time of kneading. In thisregard, when phosphorous acid (H₃PO₃) is used as the compound containingat least either PO₃ or PO₄, phosphorous acid (H₃PO₃) is added at theratio shown in Formula 3 at the time of kneading.0.05 parts by weight≦content of H₃PO₃≦5.0 parts by weight  (Formula 3)

In related art, as for the cathode active material whose compositioncontains nickel Ni, LiOH which is formed on the surface of the activematerial as an impurity is gradually carbonated in the air, and thus itis necessary to handle it carefully in the air. On the other hand,according to the embodiment, the LiOH formed on the surface of thecathode active material is converted to phosphoric acid lithium with alow reactivity by treating with phosphorous acid (H₃PO₃), therebypreventing it from absorbing carbon dioxide gas in the air.

Thus, there is provided a nonaqueous electrolyte battery which is stableas a product since expansion and deterioration of cycle characteristicsare reduced.

For example, as with the cathode 113, the anode 114 has an anode currentcollector 114A and an anode active material layer 114B that is formed onboth sides of the anode current collector 114A. The anode currentcollector 114A is made of metal foil such as copper foil.

The anode active material layer 114B include any one, or two or more ofthe anode material capable of occluding and releasing lithium as ananode active material and may also include conductive auxiliary agentsand binders, if necessary.

Examples of the anode material capable of occluding and releasinglithium include carbon materials such as graphite, non-graphitizablecarbon, or graphitizable carbon. Any one of the carbon materials may beused alone or two or more of them may be used in combination. Further,two or more of carbon materials with different mean particle diametersmay be mixed.

Further, the anode material capable of occluding and releasing lithiumis defined as an anode material capable of occluding and releasinglithium and examples thereof include materials which contain a metalelement capable of forming lithium and alloy or a metalloid element as aconstituting element. Specific examples include the simple substance,alloy, and compound of the metal element capable of forming lithium andalloy; or the simple substance, alloy, and compound of the metalloidelement capable of forming lithium and alloy; or materials having thephases of one or more such materials in at least one part thereof

Examples of the metal element or metalloid element include tin Sn, leadPb, aluminium, indium In, silicon Si, zinc Zn, antimony Sb, bismuth Bi,cadmium Cd, magnesium Mg, boron B, gallium Ga, germanium Ge, arsenic As,silver Ag, zirconium Zr, yttrium Y, or hafnium Hf. Among them, metalelements of Group 14 of the long-period periodic table or metalloidelements are preferable. A particularly preferable example is silicon Sior tin Sn. This is because silicon Si and tin Sn have a large ability toocclude and release lithium and a high energy density can be obtained.

Examples of the alloy of silicon Si include alloys containing at leastone among the group consisting of tin Sn, nickel Ni, copper Cu, iron Fe,cobalt Co, manganese Mn, zinc Zn, indium In, silver Ag, titanium Ti,germanium Ge, bismuth Bi, antimony Sb, and chromium Cr as the secondconstituting element other than silicon Si. Examples of the alloy of tinSn include alloys containing at least one among the group consisting ofsilicon Si, nickel Ni, copper Cu, iron Fe, cobalt Co, manganese Mn, zincZn, indium In, silver Ag, titanium Ti, germanium Ge, bismuth Bi,antimony Sb, and chromium Cr as the second constituting element otherthan tin Sn.

As a compound of silicon Si or a compound of tin Sn, for example, acompound containing oxygen O or carbon C is listed. In addition tosilicon Si or tin Sn, the second constituting element described abovemay be contained.

Any material may be used for the separator 115 as long it iselectrically stable, chemically stable toward the cathode activematerial, the anode active material, or the solvent and has anelectrical conductivity. For example, a nonwoven fabric made of polymer,a porous film, glass, or a paper-shaped sheet made of ceramic fibers canbe used and a plurality of them may be stacked for use. Particularly, itis preferable to use a porous polyolefin film. Further, the porouspolyolefin film may be combined with polyimide, glass, or heat-resistantmaterials made of ceramic fibers for use.

The electrolyte 116 contains an electrolytic solution and a supportcontaining a polymeric compound and is a so-called gel layer. Theelectrolytic solution contains an electrolyte salt and a solvent todissolve the electrolyte salt. Examples of the electrolyte salt includelithium salts such as LiPF₆, LiClO₄, LiBF₄, LiN(SO₂CF₃)₂, andLiN(SO₂C₂F₅)₂, and LiAsF₆. Any one of the electrolyte salts may be usedalone or two or more of them may be used in combination.

Examples of the solvent include lactone-based solvents such asγ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone;carbonate solvents such as ethylene carbonate, propylene carbonate,butylene carbonate, vinylene carbonate, dimethyl carbonate, ethyl methylcarbonate, and diethyl carbonate; ether-based solvents such as1,2-dimethoxy ethane, 1-ethoxy-2-methoxy ethane, 1,2-diethoxy ethane,tetrahydrofuran, and 2-methyl tetrahydrofuran; nitrile-based solventssuch as acetonitriles; sulfolane solvents; phosphoric acids; phosphatesolvents; or nonaqueous solvents such as pyrolidones. Any one of thesolvents may be used alone or two or more of them may be used incombination.

Further, it is preferable that a compound in which a part or all ofhydrogen atoms of a cyclic ester or chain ester is fluorinated iscontained as a solvent. Preferable examples of the fluorinated compoundto be used herein include difluoro ethylene carbonate(4,5-difluoro-1,3-dioxolane-2-on). Even when the anode 114 that containscompounds such as silicon Si, tin Sn, and germanium Ge as the anodeactive materials is used, charge-discharge cycle characteristics can beimproved.

This is because, particularly, fluoroethylene carbonate has an excellenteffect on the improvement in the cycle-characteristics.

Any polymeric compound may be used as long as it can absorb a solvent toturn into a gel. Examples thereof include fluorinated polymericcompounds such as polyvinylidene fluoride and a copolymer of vinylidenefluoride and hexa fluoro propylene; ether-based polymeric compounds suchas polyethylene oxide and a crosslinking monomer containing polyethyleneoxide; and a compound containing polyacrylonitrile, polypropylene oxide,or polymethylmethacrylate as a repeating unit. Any one of the polymericcompounds may be used alone or two or more of them may be used incombination.

Particularly, from the point of view of the redox stability, fluorinatedpolymeric compounds are desirable. Among them, a copolymer containingvinylidene fluoride and hexa fluoro propylene as components ispreferable. Additionally, the copolymer may contain a monoester of anunsaturated dibasic acid such as monomethyl maleate; halogenatedethylene such as trifluoroethylene; a cyclic ester carbonate of anunsaturated compound such as vinylene carbonate; or an acrylic vinylmonomer containing an epoxy group as a component. This is because highercharacteristics can be obtained.

Subsequently, an example of methods for manufacturing the nonaqueouselectrolyte battery according to the first embodiment will be described.

First, the cathode active material layer 113B is formed on, for example,the cathode current collector 113A and the cathode 113 is fabricated.The cathode active material layer 113B is formed as described above.Further, the anode active material layer 114B is formed on, for example,the anode current collector 114A and the anode 114 is fabricated. As forthe anode active material layer 114B, the anode active material and thebinder were mixed to prepare an anode mixture and then the anode mixturewas dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) toprovide a paste-shaped anode mixture slurry. Next, the anode mixtureslurry was applied to the anode current collector 122A and the solventwas dried, followed by compression molding with a roll presser to formthe anode active material layer 122B. Next, the cathode lead 111 ismounted on the cathode current collector 113A and the anode lead 112 ismounted on the anode current collector 114A.

Subsequently, the electrolytic solution and the polymeric compound aremixed using the combined solvent. The resulting mixed solution isapplied onto the cathode active material layer 113B and the anode activematerial layer 114B and then the combined solvent is volatilized to formthe electrolyte 116. Then, the cathode 113, separator 115, anode 114,and separator 115 are stacked sequentially in this order and then arewound. The protective tape 117 is adhered to outermost periphery thereofin order to form the spiral electrode body 110. Thereafter, the spiralelectrode body 110 is sandwiched between the exterior members 101 andthen the outer edges of the exterior members 101 are heat-sealed. Duringthe process, the adherent film 102 is inserted between the cathode lead111 and the exterior member 101, and between the anode lead 112 and theexterior member 101. Thus, the nonaqueous electrolyte battery shown inFIG. 2 is obtained.

Further, the cathode 113 and the anode 114 are not wound after formingthe electrolyte 116 thereon, but the cathode 113 and anode 114 are woundvia the separator 115 and sandwiched between the exterior members 101.Then, an electrolyte composition, which contains the electrolyticsolution and a monomer of the polymeric compound, may be injected sothat the monomer is polymerized in the exterior member 101.

When this nonaqueous electrolyte battery is charged, a lithium ion isreleased from, for example, the cathode 113 and occluded into the anode114 via the electrolyte 116. On the other hand, when the nonaqueouselectrolyte battery is discharged, a lithium ion is released from, forexample, the anode 114 and occluded into the cathode 113 via theelectrolyte 116.

As described above, according to the first embodiment, in the lithiumcomposite oxide which contains the highest proportion of nickel amongconstituent metal elements except lithium, typified by Li_(x)NiO₂, thegas generation can be inhibited by reducing LiOH and Li₂CO₃ (i.e.,impurities). Thus, the nonaqueous electrolyte battery, which has a highcapacity and a high cycle life, can be obtained.

Further, according to the first embodiment, the distribution of thebinders and the conductive auxiliary agents in the electrode is changedby treating the cathode active material with the compound containing atleast either PO₃ or PO₄ such as phosphorous acid, thereby improving thewinding characteristics of the electrode. Furthermore, since the windingcharacteristics of the electrode can be improved, the manufacture of thebattery having a flat type, as described in the first embodiment, can beachieved.

Further, a gap between the primary particles of the cathode activematerial are not filled by changing the distribution of the binders andthe conductive auxiliary agents in the electrode, thus the capacity forlarge discharge currents (load characteristics) can be improved.

Subsequently, the second embodiment will be described. With reference tothe nonaqueous electrolyte battery according to the second embodiment,an electrolytic solution is used in place of a gel electrolyte 16 in thenonaqueous electrolyte battery according to the first embodiment. Inthis case, the separator 15 is impregnated with the electrolyticsolution. In this regard, the same electrolytic solution as that of thefirst embodiment can be used.

The nonaqueous electrolyte battery having such a structure may befabricated, for example, in the following manner. The spiral electrodebody 110 is fabricated by winding the cathode 113 and the anode 114 inthe same manner as described in the first embodiment except for the gelelectrolyte 116 is not formed. The spiral electrode body 110 issandwiched between the exterior members 101. Then the electrolyticsolution is injected and the exterior member 101 is sealed.

In the second embodiment, the same effect as that of the firstembodiment can be obtained.

Next, the structure of the nonaqueous electrolyte battery according tothe third embodiment will be described with reference to FIGS. 4 and 5.FIG. 4 shows a structural example of the nonaqueous electrolyte batteryaccording to a third embodiment. This nonaqueous electrolyte battery isa so-called cylindrical shape and includes a spiral electrode body 130in which a band-shaped cathode 131 and a band-shaped anode 132 are woundvia a separator 133 in a hollow cylinder-shaped battery can 121 which isa cylinder can as an exterior member. The separator 133 is impregnatedwith an electrolytic solution which is a liquid electrolyte. The batterycan 121 is made of iron Fe plated with nickel Ni and one end thereof isclosed, and the other end is opened. In the battery can 121, a pair ofinsulating plates 122 and 123 are arranged to sandwich the spiralelectrode body 130 perpendicularly to a periphery surface thereof.

A battery lid 124, and a safety valve mechanism 125 and a positivetemperature coefficient (PTC) element 126 which are positioned insidethe battery lid 124, are mounted in the open end of the battery can 121by caulking via a gasket 127 to seal the inside of the battery can 121.The battery lid 124 is made of the same material as that of the batterycan 121. The battery lid 124 is made of the same material as the batterycan 121. The safety valve mechanism 125 is electrically connected to thebattery lid 124 through a heat sensitive resistive element 126. When aninternal pressure of the battery becomes more than certain value due tointernal short circuit or heating from outside, a disk plate 125A isinverted to cut the electric connection between the battery lid 124 andthe spiral electrode body 130. The heat sensitive resistive element 126restricts electric currents, when its resistance increases with anincrease in temperature, to prevent unusual heat generation due to highelectric currents. The gasket 127 is made of an insulating material andasphalt is applied to the surface thereof.

The spiral electrode body 130 is wound around, for example, a center pin134. A cathode lead 135 containing aluminum Al or the like is connectedto the cathode 131 of the spiral electrode body 130, and an anode lead136 containing nickel Ni or the like is connected to the anode 132. Thecathode lead 135 is welded to the safety valve mechanism 125 to beelectrically connected with the battery lid 124. The anode lead 136 iswelded to the battery can 121 to be electrically connected.

FIG. 5 is a partly enlarged cross-sectional view showing the spiralelectrode body 130 shown in FIG. 4. The spiral electrode body 130 isformed by laminating and winding the cathode 131 and the anode 132 viathe separator 133.

For example, the cathode 131 has a cathode current collector 131A and acathode active material layer 131B that is formed on both sides of thecathode current collector 131A. For example, the anode 132 has an anodecurrent collector 132A and an anode active material layer 132B that isformed on both sides of the anode current collector 132A. Each structureof the cathode current collector 131A, the cathode active material layer131B, the anode current collector 132A, the anode active material layer132B, the separator 133, and the electrolytic solution is the same asthat of the cathode current collector 113A, the cathode active materiallayer 113B, the anode current collector 114A, the anode active materiallayer 114B, the separator 115, and the electrolytic solution in thefirst embodiment.

Next, an example of the method for manufacturing the nonaqueouselectrolyte battery according to the third embodiment will be described.

The cathode 131 is fabricated in the following manner. As describedabove, the cathode active material layer 131B is formed on the cathodecurrent collector 131A to obtain the cathode 131.

The anode 132 is fabricated in the following manner. First, the anodeactive material and the binder were mixed to prepare an anode mixtureand then the anode mixture was dispersed in a solvent such asN-methyl-2-pyrrolidone to give an anode mixture slurry. Next, the anodemixture slurry was applied to the anode current collector 132A and thesolvent was dried, followed by compression molding with a roll presserto form the anode active material layer 132B. Then, the anode 132 wasfabricated.

Next, the cathode lead 135 is fixed to the cathode current collector131A with welding or the like, and the anode lead 136 is fixed to theanode current collector 132A. Thereafter, the cathode 131 and the anode132 are wound sandwiching the separator 133 therebetween, a tip portionof the cathode lead 135 is welded to the safety valve mechanism 125, atip portion of the anode lead 136 is welded to the battery can 121, andthe wound cathode 131 and anode 132 are sandwiched between a pair of theinsulating plates 122 and 123, and then housed inside the battery can121. After housing the cathode 131 and anode 132 inside the battery can121, the electrolyte is injected into the battery can 121 to beimpregnated into the separator 133. Thereafter, the battery lid 124, thesafety valve mechanism 125, and the heat sensitive resistive element 126are caulked and fixed to an opening end of the battery can 121 throughthe gasket 127. As described above, the nonaqueous electrolyte batteryshown in FIG. 4 is fabricated.

In the third embodiment, the same effect as that of the first embodimentcan be obtained. Although the cylinder can is used as the exteriormember in the third embodiment, the generation of gas is inhibited.Therefore, breakage due to the increased internal pressure that isproduced by the generation of gas can be prevented.

Next, the nonaqueous electrolyte battery according to the fourthembodiment will be described. The fourth embodiment is the nonaqueouselectrolyte battery having a square shape. As shown in FIG. 6, in thefourth embodiment, a spiral electrode body 153 is housed in an exteriorcan 151 having a square shape which is made of metals such as aluminiumAl and iron Fe. Then, an electrode pin 154 provided on a battery lid 152is connected with an electrode terminal 155 drawn from the spiralelectrode body 153 and the exterior can is closed by the battery lid152. The electrolytic solution is injected from an electrolytic solutioninlet 156, then the inlet is sealed by a sealing member 157 and thenonaqueous electrolyte battery is fabricated. In this regard, the spiralelectrode body 153 is the same as the first embodiment, a detaileddescription will not be repeated here.

In the fourth embodiment, the same effect as that of the firstembodiment can be obtained. Although the exterior can 151 having asquare shape can is used as the exterior member in the fourthembodiment, the generation of gas is inhibited. Therefore, breakage dueto the increased internal pressure that is produced by the generation ofgas can be prevented.

EXAMPLES Example 1

Composite hydroxide particles having an average composition ofCo_(0.20)N_(0.77)Al_(0.03)(OH)₂ and a mean particle diameter of 12 μmwhich was determined by the laser scattering method was mixed withcommercially available lithium hydroxide LiOH—H₂O at a molar ratio ofLi/(Co+Ni+M)=0.98, (where and M is one or more elements selected fromthe group consisting of boron B, magnesium Mg, aluminium Al, silicon Si,phosphorus P, sulfur S, titanium Ti, chromium Cr, manganese Mn, iron Fe,copper Cu, zinc Zn, gallium Ga, germanium Ge, yttrium Y, zirconium Zr,molybdenum Mo, silver Ag, barium Ba, tungsten W, indium In, tin Sn, leadPb, and antimony Sb).

The commercially available phosphorous acid (H₃PO₃) was added in anamount of 0.5 parts by weight based on the total weight of the mixedpowder, which was mixed vigorously. The resulting product was placed inan electric furnace and heated up to 470° C. in an oxygen atmosphere (ata rate of 2° C./min), followed by leaving for four hours. Further, theobtained product was heated up to 790° C. (at a rate of 2° C./min),which was left for 6 hours and then cooled to room temperature toproduce a cathode active material fired powder. The fired powders wereground so that it can pass through a mesh with an opening of 50 μm. 2parts by weight of polyvinylidene fluoride (PVdF) and 1 parts by weightof graphite were added to 97 parts by weight of composite hydroxideparticles. Then, N-methyl-2-pyrrolidone (NMP) was added thereto and wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil, which was dried and then cut into the predetermined size,and the cathode electrode in Example 1 was obtained.

Example 2

The cathode electrode in Example 2 was obtained in the same manner asdescribed in Example 1 except that composite hydroxide particles havingan average composition of Co_(0.15)Ni_(0.80)Al_(0.05)(OH)₂ was used.

Example 3

The cathode electrode in Example 3 was obtained in the same manner asdescribed in Example 3 except that composite hydroxide particles havingan average composition of Co_(0.15)Ni_(0.80)Mn_(0.05)(OH)₂ was used.

Example 4

The cathode electrode in Example 4 was obtained in the same manner asdescribed in Example 4 except that composite hydroxide particles havingan average composition of Co_(0.15)Ni_(0.80)Al_(0.04)Ba_(0.01)(OH)₂ wasused.

Example 5

The cathode electrode in Example 5 was obtained in the same manner asdescribed in Example 5 except that composite hydroxide particles havingan average composition of Co_(0.15)Ni_(0.80)Al_(0.04)Sn_(0.01)(OH)₂ wasused.

Example 6

The cathode electrode in Example 6 was obtained in the same manner asdescribed in Example 1 except that composite hydroxide particles havingan average composition of Co_(0.20)Ni_(0.80)(OH)₂ was used.

Example 7

The cathode electrode in Example 8 was obtained in the same manner asdescribed in Example 1 except that commercially available Li₃PO₄ wasadded in place of H₃PO₃.

Example 8

The cathode electrode in Example 8 was obtained in the same manner asdescribed in Example 7 except that composite hydroxide particles havingan average composition of Co_(0.15)Ni_(0.80)Al_(0.05)(OH)₂ was used.

Example 9

The cathode electrode in Example 9 was obtained in the same manner asdescribed in Example 7 except that composite hydroxide particles havingan average composition of Co_(0.15)Ni_(0.80)Mn_(0.05)(OH)₂ was used.

Example 10

The cathode electrode in Example 10 was obtained in the same manner asdescribed in Example 7 except that composite hydroxide particles havingan average composition of Co_(0.15)Ni_(0.80)Al_(0.04)Ba_(0.01)(OH)₂ wasused.

Example 11

The cathode electrode in Example 11 was obtained in the same manner asdescribed in Example 7 except that composite hydroxide particles havingan average composition of Co_(0.15)Ni_(0.80)Al_(0.04)Sn_(0.01)(OH)₂ wasused.

Example 12

The cathode electrode in Example 12 was obtained in the same manner asdescribed in Example 7 except that composite hydroxide particles havingan average composition of Co_(0.20)Ni_(0.80)(OH)₂ was used.

Example 13

2 parts by weight of polyvinylidene fluoride (PVdF) and 1 parts byweight of graphite were added to 96.8 parts by weight of composite oxideparticles having an average composition ofLi_(0.98)Co_(0.20)Ni_(0.77)Al_(0.03)O_(2.1) and a mean particle diameterof 12 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) for 1hour. Thereafter, the obtained mixture was thinly applied onto Al foil,which was dried and then cut into the predetermined size, and thecathode electrode in Example 13 was obtained.

Example 14

The cathode electrode in Example 14 was obtained in the same manner asdescribed in Example 13 except that composite oxide particles having anaverage composition of Li_(0.98)Co_(0.15)Ni_(0.80)Al_(0.05)O_(2.1) and amean particle diameter of 12 μm which was determined by the laserscattering method was used.

Example 15

The cathode electrode in Example 15 was obtained in the same manner asdescribed in Example 13 except that composite oxide particles having anaverage composition of Li_(0.98)Co_(0.15)Ni_(0.80)Mn_(0.05)O_(2.1) and amean particle diameter of 12 μm which was determined by the laserscattering method was used.

Example 16

The cathode electrode in Example 16 was obtained in the same manner asdescribed in Example 13 except that composite oxide particles having anaverage composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.04)Ba_(0.01)O_(2.1) and a mean particlediameter of 12 μm which was determined by the laser scattering methodwas used.

Example 17

The cathode electrode in Example 17 was obtained in the same manner asdescribed in Example 13 except that composite oxide particles having anaverage composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.04)Sn_(0.01)O_(2.1) and a mean particlediameter of 12 μm which was determined by the laser scattering methodwas used.

Example 18

The cathode electrode in Example 18 was obtained in the same manner asdescribed in Example 13 except that composite oxide particles having anaverage composition of Li_(0.98)Co_(0.20)Ni_(0.80)O_(2.1) and a meanparticle diameter of 12 μm which was determined by the laser scatteringmethod was used.

Example 19

The cathode electrode in Example 19 was obtained in the same manner asdescribed in Example 13 except that composite oxide particles having anaverage composition of Li_(0.98)Co_(0.28)Ni_(0.70)Al_(0.02)O_(2.1) and amean particle diameter of 12 μm which was determined by the laserscattering method was used.

Example 20

The cathode electrode in Example 20 was obtained in the same manner asdescribed in Example 13 except that composite oxide particles having anaverage composition of Li_(0.98)Co_(0.40)Ni_(0.60)O_(2.1) and a meanparticle diameter of 12 μm which was determined by the laser scatteringmethod was used.

Example 21

2 parts by weight of polyvinylidene fluoride (PVdF) and 1 parts byweight of graphite were added to 96.0 parts by weight of composite oxideparticles having an average composition ofLi_(0.98)Co_(0.20)Ni_(0.77)Al_(0.03)O_(2.1) and a mean particle diameterof 12 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP), 1.0parts by weight of H₃PO₃ was further added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil, which was dried and then cut into the predetermined size,and the cathode electrode in Example 21 was obtained.

Example 22

The cathode electrode in Example 22 was obtained in the same manner asdescribed in Example 21 except that composite oxide particles having anaverage composition of Li_(0.98)Co_(0.15)Ni_(0.80)Al_(0.05)O_(2.1) and amean particle diameter of 12 μm which was determined by the laserscattering method was used.

Example 23

The cathode electrode in Example 23 was obtained in the same manner asdescribed in Example 21 except that composite oxide particles having anaverage composition of Li_(0.98)Co_(0.15)Ni_(0.80)Mn_(0.05)O_(2.1) and amean particle diameter of 12 μm which was determined by the laserscattering method was used.

Example 24

The cathode electrode in Example 24 was obtained in the same manner asdescribed in Example 21 except that composite oxide particles having anaverage composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.04)Ba_(0.01)O_(2.1) and a mean particlediameter of 12 μm which was determined by the laser scattering methodwas used.

Example 25

The cathode electrode in Example 25 was obtained in the same manner asdescribed in Example 21 except that composite oxide particles having anaverage composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.04)Sn_(0.01)O_(2.1) and a mean particlediameter of 12 μm which was determined by the laser scattering methodwas used.

Example 26

The cathode electrode in Example 26 was obtained in the same manner asdescribed in Example 21 except that composite oxide particles having anaverage composition of Li_(0.98)Co_(0.20)Ni_(0.80)O_(2.1) and a meanparticle diameter of 12 μm which was determined by the laser scatteringmethod was used.

Example 27

The cathode electrode in Example 27 was obtained in the same manner asdescribed in Example 21 except that composite oxide particles having anaverage composition of Li_(0.98)Co_(0.28)Ni_(0.70)Al_(0.02)O_(2.1) and amean particle diameter of 12 μm which was determined by the laserscattering method was used.

Example 28

The cathode electrode in Example 28 was obtained in the same manner asdescribed in Example 21 except that composite oxide particles having anaverage composition of Li_(0.98)Co_(0.40)Ni_(0.60)O_(2.1) and a meanparticle diameter of 12 μm which was determined by the laser scatteringmethod was used.

<Comparison 1>

2 parts by weight of polyvinylidene fluoride (PVdF) and 1 parts byweight of graphite were added to 97 parts by weight of composite oxideparticles having an average composition ofLi_(0.98)Co_(0.20)Ni_(0.77)Al_(0.03)O_(2.1) and a mean particle diameterof 12 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP), 0.2parts by weight of H₃PO₃ was further added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil, which was dried and then cut into the predetermined size,and the cathode electrode in Comparison 1 was obtained.

<Comparison 2>

The cathode electrode in Comparison 2 was obtained in the same manner asdescribed in Comparison 1 except that composite oxide particles havingan average composition of Li_(0.98)Co_(0.15)Ni_(0.80)Al_(0.05)O_(2.1)and a mean particle diameter of 12 μm which was determined by the laserscattering method was used.

<Comparison 3>

The cathode electrode in Comparison 3 was obtained in the same manner asdescribed in Comparison 1 except that composite oxide particles havingan average composition of Li_(0.98)Co_(0.15)Ni_(0.80)Mn_(0.05)O_(2.1)and a mean particle diameter of 12 μm which was determined by the laserscattering method was used.

<Comparison 4>

The cathode electrode in Comparison 4 was obtained in the same manner asdescribed in Comparison 1 except that composite oxide particles havingan average composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.04)Ba_(0.01)O_(2.1) and a mean particlediameter of 12 μm which was determined by the laser scattering methodwas used.

<Comparison 5>

The cathode electrode in Comparison 5 was obtained in the same manner asdescribed in Comparison 1 except that composite oxide particles havingan average composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.04)Sn_(0.01)O_(2.1) and a mean particlediameter of 12 μm which was determined by the laser scattering methodwas used.

<Comparison 6>

The cathode electrode in Comparison 6 was obtained in the same manner asdescribed in Comparison 1 except that composite oxide particles havingan average composition of Li_(0.98)Co_(0.20)Ni_(0.80)O_(2.1) and a meanparticle diameter of 12 μm which was determined by the laser scatteringmethod was used.

<Comparison 7>

2% of polyvinylidene fluoride (PVdF) and 1% of graphite were added tocomposite oxide particles having an average composition ofLi_(1.01)Co_(0.99)Al_(0.01)O_(2.1) and a mean particle diameter of 11 μmwhich was determined by the laser scattering method. The resultingmixture was well kneaded with N-methyl-2-pyrrolidone (NMP) for 1 hour.Thereafter, the obtained mixture was thinly applied onto Al foil, whichwas dried and then cut into the predetermined size, and the cathodeelectrode in Comparison 7 was obtained.

<Comparison 8>

2 parts by weight of polyvinylidene fluoride (PVdF) and 1 parts byweight of graphite were added to 96.8 parts by weight of composite oxideparticles having an average composition ofLi_(1.01)Co_(0.99)Al_(0.01)O_(2.1) and a mean particle diameter of 12 μmwhich was determined by the laser scattering method. While the resultingmixture was kneaded with N-methyl-2-pyrrolidone (NMP) and further 0.2parts by weight of H₃PO₃ was added thereto, which was well kneaded for 1hour. Thereafter, the obtained mixture was thinly applied onto Al foil,which was dried and then cut into the predetermined size, and thecathode electrode in Comparison 8 was obtained.

A laminated cell (a size of 542436 and a rating of 1000 mAh) wasfabricated by using the cathode electrodes in Examples 1 to 28 andComparisons 1 to 8 and laminating an outer face with aluminum. Further,a laminated cell (a size of 542436 and a rating of 920 mAh) wasfabricated by using the cathode electrodes in Comparisons 7 and 8 andlaminating an outer face with aluminum. In this regard, the usedelectrolytic solution had a composition in which LiPF was dissolved in amixed solvent prepared by mixing ethylene carbonate (EC) and diethylcarbonate (DEC) at a weight ratio of EC:DEC=3:7 so as to be LiPF₆1mol/kg and further 5 parts by weight of vinylene carbonate (VC) wasadded thereto.

Next, the laminated cell thus fabricated was subjected to the followingexpansion test as well as charge and discharge test and the amount ofexpansion and the capacity maintenance rate after 500 cycles weredetermined.

(Expansion Test)

The laminated cell was subjected to two cycles of charge and dischargeat 23° C. Then, it was charged to 4.2 V at 23° C. and the thickness(initial thickness) of the battery was measured. Thereafter, the storagetest was carried out in a thermostat at 90° C. After 4 hours, thethickness of the battery was determined and then difference between thethickness and the initial thickness was found. In this regard, thecharging was performed at a constant current of 0.5 C under a constantvoltage condition (up to the upper limit voltage of 4.2 V) and thedischarging was performed at a constant current of 0.2 C (up to thefinal voltage of 2.5 V).

(Charge and Discharge Test)

The capacity maintenance rate was determined by the ratio of thedischarge capacity of the 500th cycle at 23° C. to the dischargecapacity of the 1st cycle at 23° C., namely, (“discharge capacity of the500th cycle at 23° C.”/“discharge capacity of the 1st cycle at 23°C.”)×100. In this regard, the charging was performed at a constantcurrent of 1 C under a constant voltage condition (up to the upper limitvoltage of 4.2 V) and the discharging was performed at a constantcurrent of 1 C (up to the final voltage of 2.5 V).

Further, as for the cathode electrode in Example and Comparison, theconcentration analysis of the carbonic acid content of the cathodeactive material was performed in accordance with the method shown inJIS-R-9101.

The measured results and the concentration analysis results of carbonicacid content are shown in Table 1.

TABLE 1 CAPACITY MAINTENANCE CARBONIC COMPOSITION OF CATHODE ADDITIONAMOUNT OF RATE AFTER ACID ACTIVE MATERIAL (MOLAR RATIO) AMOUNT EXPANSION500 CYCLES CONTENT Ni Co Al Mn Ba Sn ADDITIVE [wt %] [mm] [%] CO₃ ²⁻[wt%] EXAMPLE 1 77 20 3 — — — H₃PO₃ 0.5 0.7 77.0 0.17 EXAMPLE 2 80 15 5 — —— H₃PO₃ 0.5 0.5 75.0 0.18 EXAMPLE 3 80 15 — 5 — — H₃PO₃ 0.5 0.5 75.00.18 EXAMPLE 4 80 15 4 — 1 — H₃PO₃ 0.5 0.5 75.2 0.18 EXAMPLE 5 80 15 4 —— 1 H₃PO₃ 0.5 0.5 75.3 0.18 EXAMPLE 6 80 20 — — — — H₃PO₃ 0.5 0.8 74.00.13 EXAMPLE 7 77 20 3 — — — Li₃PO₄ 0.5 1.2 76.0 0.21 EXAMPLE 8 80 15 5— — — Li₃PO₄ 0.5 1.0 74.6 0.20 EXAMPLE 9 80 15 — 5 — — Li₃PO₄ 0.5 1.073.1 0.20 EXAMPLE 10 80 15 4 — 1 — Li₃PO₄ 0.5 1.0 73.0 0.20 EXAMPLE 1180 15 4 — — 1 Li₃PO₄ 0.5 1.0 73.8 0.20 EXAMPLE 12 80 20 — — — — Li₃PO₄0.5 1.1 72.0 0.21 EXAMPLE 13 77 20 3 — — — H₃PO₃ 0.2 0.8 82.0 0.19EXAMPLE 14 80 15 5 — — — H₃PO₃ 0.2 0.9 81.0 0.19 EXAMPLE 15 80 15 — 5 —— H₃PO₃ 0.2 0.9 81.5 0.19 EXAMPLE 16 80 15 4 — 1 — H₃PO₃ 0.2 0.9 81.20.19 EXAMPLE 17 80 15 4 — — 1 H₃PO₃ 0.2 0.9 81.0 0.19 EXAMPLE 18 80 20 —— — — H₃PO₃ 0.2 1.0 80.0 0.20 EXAMPLE 19 70 28 2 — — — H₃PO₃ 0.2 0.879.4 0.18 EXAMPLE 20 60 40 — — — — H₃PO₃ 0.2 0.7 79.2 0.17 EXAMPLE 21 7720 3 — — — H₃PO₃ 1.0 0.5 74.0 0.14 EXAMPLE 22 80 15 5 — — — H₃PO₃ 1.00.5 73.4 0.14 EXAMPLE 23 80 15 — 5 — — H₃PO₃ 1.0 0.5 73.1 0.14 EXAMPLE24 80 15 4 — 1 — H₃PO₃ 1.0 0.5 73.0 0.14 EXAMPLE 25 80 15 4 — — 1 H₃PO₃1.0 0.5 73.7 0.14 EXAMPLE 26 80 20 — — — — H₃PO₃ 1.0 0.6 72.5 0.16EXAMPLE 27 70 28 2 — — — H₃PO₃ 1.0 0.5 73.2 0.14 EXAMPLE 28 60 40 — — —— H₃PO₃ 1.0 0.4 74.3 0.13 COMPARISON 1 77 20 3 — — — NONE — 5.0 21.00.40 COMPARISON 2 80 15 5 — — — NONE — 6.4 14.0 0.60 COMPARISON 3 80 15— 5 — — NONE — 6.0 10 OR LESS 0.41 COMPARISON 4 80 15 4 — 1 — NONE — 6.010 OR LESS 0.42 COMPARISON 5 80 15 4 — — 1 NONE — 6.0 10 OR LESS 0.42COMPARISON 6 80 20 — — — — NONE — 7.6 10 OR LESS 0.45 COMPARISON 7 — 991 — — — NONE — 0.7 77.0 0.07 COMPARISON 8 — 99 1 — — — H₃PO₃ 0.2 0.773.2 0.07

As shown in Table 1, in the case of Examples 1 to 28 as compared to thecase of Comparisons 1 to 6, it was found that the amount of expansioncould be remarkably reduced and further the capacity maintenance ratecould be significantly improved.

When Comparison 7 was compared to Comparison 8, it was found that, asfor the cathode active material not containing nickel, the amount ofexpansion and the capacity maintenance rate in the case of a batterywhich was fabricated by using the cathode formed by adding phosphoruscompound as an additive are nearly equal to those in the case of abattery which was fabricated by using the cathode formed without addingphosphorus compound as an additive.

Further, the cathode mixture slurry used was the same as that inExamples 6, 12, 18, 24, and Comparison 6. The bending test was performedin order to examine the winding characteristics of the electrode in thecase where the amount and type of additive agent is changed. The bendingtest was performed in the following manner. Polyvinylidene fluoride(PVdF) as a binder, ketjen black as a conductive auxiliary agent, andN-methyl-2-pyrrolidone (NMP) were added to the synthesized cathodeactive material, which was kneaded and then applied to both sides ofaluminum foil 15 μm thick, followed by drying sufficiently in order tovolatilize N-methyl-2-pyrrolidone (NMP). After drying, the cathodeactive material was pressed so as to be a predetermined volume density.Further, the coated foil (electrode) after pressing was subjected tovacuum drying. Thereafter, the foil was bent in half and the occurrenceof breakage, cracking, or cutting was visually confirmed. Test resultsare shown in Table 2. In Table 2, the evaluation of breakage or crackingof a coated foil (electrode) is indicated by a “∘” mark or a “×” mark.

TABLE 2 COMPOSITION OF CATHODE ACTIVE THICKNESS MATERIAL ADDITION OFVOLUME DENSITY (MOLAR RATIO) AMOUNT ELECTRODE [g/cm³] Ni Co ADDITIVE [wt%] [μm] 3.20-3.25 3.30-3.35 3.40-3.45 EXAMPLE 6 80 20 H₃PO₃ 0.5 146 ∘∘∘∘∘∘ ∘∘∘ EXAMPLE 12 80 20 Li₃PO₄ 0.5 145 ∘∘∘ ∘∘∘ ∘∘∘ EXAMPLE 18 80 20H₃PO₃ 0.2 147 ∘∘∘ ∘∘∘ ∘∘∘ EXAMPLE 24 80 20 H₃PO₃ 1.0 146 ∘∘∘ ∘∘∘ ∘∘∘COMPARISON 6 80 20 NONE — 145 ∘∘∘ xxx xxx *∘: CUTTING OR CRACKING OFELECTRODES ARE NOT OBSERVED x: CUTTING OR CRACKING OF ELECTRODES AREOBSERVED

As shown in Table 2, in the cathodes of Examples 6, 12, 18, and 24,cutting or cracking of the electrodes was not occurred even when thevolume density is in a range of 3.30 g/cm³ to 3.35 g/cm³ or in a rangeof 3.40 g/cm³ to 3.45 g/cm³. On the other hand, cutting or cracking ofthe electrodes was occurred in Comparison 6.

Further, the load characteristics were measured using the laminated cellproduced by using the cathode electrode in Example 13 and Comparison 1.The measured results are shown in FIGS. 7A and 7B. FIG. 7A shows themeasured results of the laminated cell produced by using the cathodeelectrode in Example 13. FIG. 7B shows the measured results of thelaminated cell produced by using the cathode electrode in Comparison 1.In this regard, the measurement was carried out in a temperatureenvironment of 23° C., the charging was performed at a constant currentof 0.2C under a constant voltage condition (up to the upper limitvoltage of 4.2 V), and the discharging was performed at constantcurrents of 0.2 C, 0.5 C, 1.0 C, 2.0 C, and 3.0 C (up to the finalvoltage of 2.5 V).

As shown in FIGS. 7A and 7B, it was found that the capacity for largedischarge currents in the laminated cell produced using the cathode inExample 13 could be highly improved as compared to that of the laminatedcell produced using the cathode in Comparison 1.

Further, the cathode electrode was observed with an electron microscope.Electron micrographs of the surface of the cathode electrode in Example13 and Comparison 1 is shown in FIGS. 8A and 8B. FIG. 8A is an electronmicrograph of the surface of the cathode electrode in Example 13. FIG.8B is an electron micrograph of the surface of the cathode electrode inComparison 1. On the surface of Comparison 1, the binder and theconductive auxiliary agent (black colored area) are incorporated into agap between the primary particles of the cathode active material (grayarea) and a net shape is formed. On the other hand, in Example 13, thebinder and the conductive auxiliary agent are hardly incorporated into agap between the primary particles. It is considered that lower amountsof the binder and the conductive auxiliary agent between primaryparticles allow lithium ions to move easily.

Further, the electrode surface in Example 21 and Comparison 1 wasdetermined by Time-of-Flight secondary Ion Mass Spectrometry (TOF-SIMS).The results of the cathode electrode in Example 21 and Comparison 1which are determined based on TOF-SIMS positive secondary ion massspectrometry are shown in FIGS. 9A and 9B as well as FIGS. 10A and 10B.The results of the cathode electrode in Example 21 and Comparison 1,which are determined based on TOF-SIMS negative secondary ion massspectrometry, are shown in FIG. 11.

As shown in FIGS. 9 to 11, a peak of a fragment based on positivesecondary ions of C₃F₅, C₅F₉, C₇F₁₃, and Li₄PO₄ and negative secondaryions of PO₂, PO₃, LiP₂O₄, LiP₂O₅, LiP₂O₆, LiPO₂F, LiPO₃F, POF₂, PO₂F₂,and LiPO₃H was observed.

In addition, the results of the surface analysis by X-ray photoelectronspectroscopy in Example 21 and Comparison 1 are shown in FIG. 12. Theline a shows the analysis results of the cathode electrode before thecharging and discharging in Example 21. The line b shows the analysisresults of the cathode electrode after the first charging anddischarging in Example 21. The line c shows the analysis results of thecathode electrode after the first charging and discharging inComparison 1. Here, the cathode electrode after the first charging anddischarging is the cathode electrode which is washed with dimethylcarbonate (DMC) after dismounting of the battery, followed by vacuumdrying at 50° C.

As shown in FIG. 12, the P 2p spectrum derived from LiPF₆ in theelectrolytic solution used for the battery was also observed after thefirst charging and discharging in Comparison 1, where phosphorous acidwas not added. The difference between Comparison 1 and Example 21 isclear from the difference of the peak intensity and a peak in the P 2pspectrum derived from the phosphorus compound contained in the cathodecan be confirmed.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof. Forexample, the cathode active material layer 13B may contain other cathodeactive materials in addition to the cathode active materials describedabove.

Examples of other cathode active materials include a lithium cobaltcomposite oxide having a rock-salt layer structure that contains lithiumand cobalt, and a lithium manganese composite oxide having a spinelstructure that contains lithium and manganese.

In addition, a so-called lithium-ion secondary battery in which thecapacity of the anode is represented by a capacity component determinedby occlusion and release of lithium has been described in theabove-mentioned embodiments and Examples. The present application can besimilarly applied to a so-called lithium metal secondary battery inwhich lithium metal is used for the anode active material and thecapacity of the anode is represented by a capacity component determinedby precipitation and dissolution of lithium. Further, the presentapplication can be similarly applied to a secondary battery in which thecapacity of the anode is represented by the sum of the capacitycomponent determined by occlusion and release of lithium and thecapacity component determined by precipitation and dissolution oflithium by lowering the charging capacity of the anode material capableof occluding and releasing lithium than the charging of the cathode.

Furthermore, the case where the present application is applied to thesecondary batteries of a flat type, a cylindrical type, and a squaretype has been described in the above-mentioned embodiments and Examples.The present application can be similarly applied to the secondarybatteries of a button type, a thin type, a large type, and a stackedlamination type. Further, the present application can be applied to notonly the secondary batteries but also primary batteries.

Subsequently, the fifth embodiment of the present application will bedescribed with reference to the accompanying drawings. A method formanufacturing a cathode according to the fifth embodiment includes thesteps of: mixing phosphorous acid (H₃PO₃) with cathode active materialto prepare a cathode mixture slurry; and applying the cathode mixtureslurry to a cathode current collector to form a cathode active materiallayer.

With reference to the method for manufacturing a cathode according tothe fifth embodiment, the cathode active material is mixed withphosphorous acid (H₃PO₃) when preparing the cathode mixture slurry, andthus the distribution of binders and conductive auxiliary agents in thecathode active material layer is changed at the time of coating anddrying the cathode mixture slurry, which allows for improving thewinding characteristics of an electrode.

As the cathode active material, a lithium composite oxide capable ofoccluding and releasing lithium can be used. Specific examples of thelithium composite oxide to be used herein include the lithium compositeoxides having an average composition represented by Formula I andfurther preferable examples thereof include lithium composite oxideshaving an average composition represented by Formula II which containthe highest proportion of nickel Ni among constituent metal elementsexcept lithium:Li_(x)Co_(y)Ni_(z)M_(1-y-z)O_(b-a)X_(a)  (Chemical formula I)

wherein M is one or more elements selected from the group consisting ofboron B, magnesium Mg, aluminium Al, silicon Si, phosphorus P, sulfur S,titanium Ti, chromium Cr, manganese Mn, iron Fe, copper Cu, zinc Zn,gallium Ga, germanium Ge, yttrium Y, zirconium Zr, molybdenum Mo, silverAg, barium Ba, tungsten W, indium In, tin Sn, lead Pb, and antimony Sb;X is halogen; and x, y, z, a, and b are values in the range of0.8<x≦1.2, 0≦y≦1.0, 0≦z≦1.0, 1.8≦b≦2.2, and 0≦a≦1.0, respectively,Li_(x)Co_(y)Ni_(z)M_(1-y-z)O_(b-a)X_(a)  (Chemical formula II)

wherein M is one or more elements selected from the group consisting ofboron B, magnesium Mg, aluminium Al, silicon Si, phosphorus P, sulfur S,titanium Ti, chromium Cr, manganese Mn, iron Fe, copper Cu, zinc Zn,gallium Ga, germanium Ge, yttrium Y, zirconium Zr, molybdenum Mo, silverAg, barium Ba, tungsten W, indium In, tin Sn, lead Pb, and antimony Sb;X is halogen; and x, y, z, a, and b are values in the range of0.8<x≦1.2, 0≦y≦0.5, 0.5≦z≦1.0, 1.8≦b≦2.2, and 0≦a≦1.0, respectively.

Usable examples of the binder include polyvinylidene fluoride (PVdF),and polytetrafluoroethylene. Usable examples of the conductive auxiliaryagent include carbon powders such as graphite and carbon black.

Phosphorous acid (H₃PO₃) is added at the time of kneading the cathodeactive material with binders such as polyvinylidene fluoride (PVdF) andsolvents such as N-methyl-2-pyrrolidone (NMP). In this regard,conductive auxiliary agents such as graphite may be added at the time ofthe kneading.

The addition amount of phosphorous acid (H₃PO₃) is set to 0.01 parts byweight or more and 5.0 parts by weight or less to 100 parts by weight ofcathode active material. When the addition amount of phosphorous acid(H₃PO₃) is less than 0.01 parts by weight, the obtained effect is notsufficient. When the addition amount exceeds 5.0 parts by weight, thecathode active material is peeled off from aluminum foil of thecollector, and thus it is difficult to press or wind.

It is preferable that the addition amount of phosphorous acid (H₃PO₃) is0.05 parts by weight or more and 5.0 parts by weight or less to 100parts by weight of cathode active material, in the case where a lithiumcomposite in which the content of nickel Ni is higher than that ofcobalt Co, among lithium composites having an average compositionrepresented by Formula I, is contained as a cathode active material.This is because more excellent winding characteristics as well assufficient cycle characteristics can be obtained in the range.

It is preferable that the addition amount of phosphorous acid (H₃PO₃) is0.01 parts by weight or more and 1.0 parts by weight or less to 100parts by weight of cathode active material, in the case where a lithiumcomposite in which the content of nickel Ni is lower than that of cobaltCo, among lithium composites having an average composition representedby Formula I, is contained as a cathode active material. This is becausemore excellent winding characteristics as well as sufficient cyclecharacteristics can be obtained in the range.

With reference to the method for manufacturing a cathode according tothe fifth embodiment, the distribution of binders and conductiveauxiliary agents in the electrode is changed by adding phosphorous acid(H₃PO₃), which allows for improving the winding characteristics of anelectrode.

Since the binders and the conductive auxiliary agents are distributed inthe electrode so as not to fill a gap between the primary particles ofthe cathode active material, the capacity for large discharge currents(load characteristics) can be improved.

Further, in the lithium composite oxide whose composition containsnickel Ni, LiOH, which is formed on the surface of the active materialas an impurity, is gradually carbonated in the air, and thus it isnecessary to handle it carefully in the air. In the manufacture method acathode according to an embodiment, the LiOH formed on the surface oflithium composite oxide is converted to phosphoric acid lithium with alow reactivity by treating with phosphorous acid (H₃PO₃), therebypreventing it from absorbing carbon dioxide gas in the air. Thus, thereis provided a nonaqueous electrolyte battery which is stable as aproduct since expansion and deterioration of cycle characteristics arereduced.

An example of the nonaqueous electrolyte secondary battery that isformed by using the cathode produced by the above-mentionedmanufacturing method will be described. FIG. 13 is a perspective viewshowing the first example of the nonaqueous electrolyte battery. Thenonaqueous electrolyte battery is, for example, a nonaqueous electrolytesecondary battery. The nonaqueous electrolyte battery has the spiralelectrode body 210 on which the cathode lead 211 and the anode lead 212are mounted in a film-shaped exterior member 201 and has a flat type.

Each of the cathode lead 211 and the anode lead 212 has a stripe-shaped,and is drawn, respectively from the inside of the exterior member 201 tothe outside, for example, in the same direction. The cathode lead 211 ismade of metallic materials such as aluminium Al and the anode lead 212is made of metallic materials such as nickel Ni.

The exterior member 201 is a laminated film having a structure in which,for example, the insulating layer, the metal layer, and the outermostare stacked sequentially in this order and then combined by lamination.In the exterior member 201, for example, the insulating layer is facedinwardly and the respective outer edges are bonded by welding or byusing adhesives.

The insulating layer is made of polyethylene, polypropylene, modifiedpolyethylene, modified polypropylene or polyolefin resins such ascopolymers thereof This is because the moisture permeability isdecreased and an excellent airtightness is provided. The metal layer ismade of aluminium Al, stainless steel SUS, nickel Ni, or iron Fe infoil-shaped or plate form.

The outermost layer may be made of, for example, the same resin as thatof the insulating layer and further may be made of nylon. This isbecause resistance to breakage or sticking can be improved. The exteriormember 1 may include other layers in addition to the insulating layer,the metal layer, and the outermost layer.

In order to improve the adhesion of the cathode lead 211 and the anodelead 212 to the inside of the exterior member 201 and prevent outsideair from entering, an adherent film 202 is inserted between the exteriormember 201 and the cathode lead 211, and between the exterior member 201and the anode lead 212. The adherent film 202 is made of a materialhaving adhesion to the cathode lead 211 and the anode lead 212. Forexample, the adherent film is preferably made of polyolefin resins suchas polyethylene, polypropylene, modified polyethylene, or modifiedpolypropylene in the case where the cathode lead 211 and the anode lead212 is made of the metallic materials described above.

FIG. 14 is a cross-sectional view along the line II-II of the spiralelectrode body 210 shown in FIG. 13. The spiral electrode body 210 isformed by stacking a cathode 213 and an anode 214 via a separator 215and an electrolyte 216 and winding them. The outermost periphery thereofis protected by a protective tape 217.

For example, the cathode 213 has a cathode current collector 213A and acathode active material layer 213B that is formed on both sides of thecathode current collector 213A. The cathode current collector 213A ismade of metal foil such as aluminum foil.

The cathode active material layer 213B includes the cathode activematerial that has the lithium composite oxide and the phosphoruscompound which is contained near the surface of the lithium compositeoxide. In addition, the cathode active material layer 13B includes theconductive auxiliary agent such as the carbon material; and the bindersuch as polyvinylidene fluoride (PVdF) or polytetrafluoroethylene.

The phosphorus compound is a compound in which the binding energy peakin the P 2p spectrum based on X-ray photoelectron spectroscopy (XPS) isin the range of 132 to 135 eV. At least a part of the phosphoruscompound is represented by, for example, Formula III or IV:Li_(c)Co_(d)H_(e)P_(f)O_(g)  (Chemical formula III)

wherein c, e, and f represent an integer of 1 or more; and d and erepresent an integer of 0 or more,Li_(g)PO_(h)F_(i)  (Chemical formula IV)

wherein g, h, and i represent an integer of 1 or more.

These phosphorus compounds are present near the surface of lithiumcomposite oxide particles, for example, it is present so as to cover thelithium compound oxide particles. As a method for confirming that thesephosphorus compounds are present near the surface of lithium compositeoxide particles, for example, a method in which the cathode 213 isembedded in resin and then the distribution in the cross section isdetermined by Time-of-Flight secondary Ion Mass Spectrometry (TOF-SIMS)is listed. Alternatively, it can be confirmed by analyzing elements byX-ray photoelectron spectroscopy while the cathode surface is spatteredwith argon.

The cathode active material layer 213B has a peak of a fragment of atleast one secondary ion selected from the group consisting of positivesecondary ions of Li₄PO₄, C₃F₅, C₅F₉, C₇F₁₃, negative secondary ions ofPO₂, PO₃, LiP₂O₄, LiP₂O₅, LiP₂O₆, LiPO₂F, LiPO₃F, POF₂, PO₂F₂, andLiPO₃H based on the surface analysis by Time-of-Flight secondary IonMass Spectrometry (TOF-SIMS) is observed near the surface.

The cathode active material layer 213B has a peak of a fragment of atleast one secondary ion selected from the group consisting of positivesecondary ions of Li₄PO₄, Li₂CoPO₄, Li₂CoPH₂O₄, Li₃CoPO₄, and Li₃CoPO₄H,negative secondary ions of PO₂, LiP₂O₄, Co₂PO₄, CoP₂O₅, CoP₂O₅H, CoP₂O₆,and CoP₂O₆H based on the surface analysis by TOF-SIMS.

It is preferable that the thickness of the cathode 213 is 250 μm orless.

For example, as with the anode 213, the anode 214 has an anode currentcollector 214A and an anode active material layer 214B that is formed onboth sides of the anode current collector 214A. The anode currentcollector 214A is made of metal foil such as copper foil.

The anode active material layer 214B include any one, or two or more ofthe anode material capable of occluding and releasing lithium as ananode active material and may also include conductive auxiliary agentsand binders, if necessary.

Examples of the anode material capable of occluding and releasinglithium include carbon materials such as graphite, non-graphitizablecarbon, or graphitizable carbon. Any one of the carbon materials may beused alone or two or more of them may be used in combination. Further,two or more of carbon materials with different mean particle diametersmay be mixed.

Further, the cathode material capable of occluding and releasing lithiumis defined as a cathode material capable of occluding and releasinglithium and examples thereof include materials which contain a metalelement capable of forming lithium and alloy or a metalloid element as aconstituting element. Specific examples include the simple substance,alloy, and compound of the metal element capable of forming lithium andalloy; or the simple substance, alloy, and compound of the metalloidelement capable of forming lithium and alloy; or materials having thephases of one or two or more kinds of such materials in at least onepart thereof.

Examples of the metal element or metalloid element include tin Sn, leadPb, aluminium, indium In, silicon Si, zinc Zn, antimony Sb, bismuth Bi,cadmium Cd, magnesium Mg, boron B, gallium Ga, germanium Ge, arsenic As,silver Ag, zirconium Zr, yttrium Y, or hafnium Hf. Among them, metalelements of Group 14 of the long-period periodic table or metalloidelements are preferable. A particularly preferable example is silicon Sior tin Sn. This is because silicon Si and tin Sn have a large ability toocclude and release lithium and a high energy density can be obtained.

Examples of the alloy of silicon Si include alloys containing at leastone among the group consisting of tin Sn, nickel Ni, copper Cu, iron Fe,cobalt Co, manganese Mn, zinc Zn, indium In, silver Ag, titanium Ti,germanium Ge, bismuth Bi, antimony Sb, and chromium Cr as the secondconstituting element other than silicon Si. Examples of the alloy of tinSn include alloys containing at least one among the group consisting ofsilicon Si, nickel Ni, copper Cu, iron Fe, cobalt Co, manganese Mn, zincZn, indium In, silver Ag, titanium Ti, germanium Ge, bismuth Bi,antimony Sb, and chromium Cr as the second constituting element otherthan tin Sn.

As a compound of silicon Si or a compound of tin Sn, for example, acompound containing oxygen O or carbon C is listed. In addition tosilicon Si or tin Sn, the second constituting element described abovemay be contained.

Any material may be used for the separator 215 as long it iselectrically stable, chemically stable toward the cathode activematerial, the anode active material, or the solvent and has anelectrical conductivity. For example, a nonwoven fabric made of polymer,a porous film, glass, or a paper-shaped sheet made of fibers of ceramicscan be used and a plurality of them may be stacked for use.Particularly, it is preferable to use a porous polyolefin film. Further,the porous polyolefin film may be combined with polyimide, glass, orheat-resistant materials made of ceramic fibers for use.

The electrolyte 216 contains an electrolytic solution and a supportcontaining a polymeric compound and is the so-called gel layer. Theelectrolytic solution contains an electrolyte salt and a solvent todissolve the electrolyte salt. Examples of the electrolyte salt includelithium salts such as LiPF₆, LiClO₄, LiBF₄, LiN(SO₂CF₃)₂, andLiN(SO₂C₂F₅)₂, and LiAsF₆. Any one of the electrolyte salts may be usedalone or two or more of them may be used in combination.

Examples of the solvent include lactone-based solvents such asγ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone;carbonate solvents such as ethylene carbonate, propylene carbonate,butylene carbonate, vinylene carbonate, dimethyl carbonate, ethyl methylcarbonate, and diethyl carbonate; ether-based solvents such as1,2-dimethoxy ethane, 1-ethoxy-2-methoxy ethane, 1,2-diethoxy ethane,tetrahydrofuran, and 2-methyl tetrahydrofuran; nitrile-based solventssuch as acetonitriles; sulfolane solvents; phosphoric acids; phosphatesolvents; or nonaqueous solvents such as pyrolidones. Any one of thesolvents may be used alone or two or more of them may be used incombination.

Further, it is preferable that a compound in which a part or all ofhydrogen atoms of a cyclic ester or chain ester is fluorinated iscontained as a solvent. Preferable examples of the fluorinated compoundto be used herein include difluoro ethylene carbonate(4,5-difluoro-1,3-dioxolane-2-on). Even when the anode 114 that containscompounds such as silicon Si, tin Sn, and germanium Ge as the anodeactive materials is used, charge-discharge cycle characteristics can beimproved.

This is because, particularly, fluoroethylene carbonate has an excellenteffect on the improvement in the cycle-characteristics.

Any polymeric compound may be used as long as it can absorb a solvent toturn into a gel. Examples thereof include fluorinated polymericcompounds such as polyvinylidene fluoride and a copolymer of vinylidenefluoride and hexa fluoro propylene; ether-based polymeric compounds suchas polyethylene oxide and a crosslinking monomer containing polyethyleneoxide; and a compound containing polyacrylonitrile, polypropylene oxide,or polymethylmethacrylate as a repeating unit. Any one of the polymericcompounds may be used alone or two or more of them may be used incombination.

Particularly, from the point of view of the redox stability, fluorinatedpolymeric compounds are desirable. Among them, a copolymer containingvinylidene fluoride and hexa fluoro propylene as components ispreferable. Additionally, the copolymer may contain a monoester of anunsaturated dibasic acid such as monomethyl maleate; halogenatedethylene such as trifluoroethylene; a cyclic ester carbonate of anunsaturated compound such as vinylene carbonate; or an acrylic vinylmonomer containing an epoxy group as a component. This is because highercharacteristics can be obtained.

Hereinafter, the method for manufacturing the nonaqueous electrolytebattery of the first example will be described.

First, the cathode active material layer 213B is formed on, for example,the cathode current collector 213A and the cathode 213 is fabricated.Since the formation method of the positive active material layer 213Bhas been described, a detailed description will not be repeated here.Further, the anode active material layer 214B is formed on, for example,the anode current collector 214A and the anode 214 is fabricated. As forthe anode active material layer 214B, the anode active material and thebinder were mixed to prepare an anode mixture and then the anode mixturewas dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) toprovide a paste-shaped anode mixture slurry.

Next, the anode mixture slurry was applied to the anode currentcollector 222A and the solvent was dried, followed by compressionmolding with a roll presser to form the anode active material layer222B. Then, the anode 222 was fabricated. Next, the cathode lead 211 ismounted on the cathode current collector 213A and the anode lead 212 ismounted on the anode current collector 214A.

Subsequently, the electrolytic solution and the polymeric compound aremixed using the combined solvent. The resulting mixed solution isapplied onto the cathode active material layer 213B and the anode activematerial layer 214B and then the combined solvent is volatilized to formthe electrolyte 216. Then, the cathode 213, separator 215, anode 214,and separator 215 are stacked sequentially in this order and then arewound. The protective tape 217 is adhered to outermost periphery thereofin order to form the spiral electrode body 210. Thereafter, the spiralelectrode body 210 is sandwiched between the exterior members 201 andthen the outer edges of the exterior members 201 are heat-sealed. Duringthe process, the adherent film 202 is inserted between the cathode lead211 and the exterior member 201, and between the anode lead 212 and theexterior member 201. Thus, the nonaqueous electrolyte battery shown inFIG. 13 is obtained.

Further, the cathode 213 and the anode 214 are not wound after formingthe electrolyte 216 thereon, but the cathode 213 and anode 214 are woundvia the separator 215 and sandwiched between the exterior members 201.Then, an electrolyte composition, which contains the electrolyticsolution and a monomer of the polymeric compound, may be injected sothat the monomer is polymerized in the exterior member 201.

When this nonaqueous electrolyte battery is charged, a lithium ion isreleased from, for example, the cathode 213 and occluded into the anode214 via the electrolyte 216. On the other hand, when the nonaqueouselectrolyte battery is discharged, a lithium ion is released from, forexample, the anode 214 and occluded into the cathode 213 via theelectrolyte 216.

Next, the second example of the nonaqueous electrolyte battery will bedescribed. With reference to the nonaqueous electrolyte batteryaccording to the second example, an electrolytic solution is used inplace of the gel electrolyte 216 in the nonaqueous electrolyte batteryaccording to the first example. In this case, the separator 215 isimpregnated with the electrolytic solution. The same electrolyticsolution as that of the first example of the nonaqueous electrolytebattery can be used.

The nonaqueous electrolyte battery having such a structure may befabricated, for example, in the following manner. The spiral electrodebody 210 is fabricated by winding the cathode 213 and the anode 214 inthe same manner as described in the first example of the nonaqueouselectrolyte battery except for the gel electrolyte 216 is not formed.The spiral electrode body 210 is sandwiched between the exterior members201. Then the electrolytic solution is injected and the exterior member201 is sealed.

The structure of the third example of the nonaqueous electrolyte batterywill be described with reference to FIGS. 15 and 16.

FIG. 15 shows structure of the third example of the nonaqueouselectrolyte battery. This nonaqueous electrolyte battery is theso-called cylindrical shape and includes a spiral electrode body 230 inwhich a band-shaped cathode 231 and a band-shaped anode 232 are woundvia a separator 233 in a hollow cylinder-shaped battery can 221 which isa cylinder can as the exterior member 201. The separator 233 isimpregnated with an electrolytic solution which is a liquid electrolyte.The battery can 221 is made of iron Fe plated with nickel Ni and one endthereof is closed, and the other end is opened. In the battery can 221,a pair of insulating plates 222 and 223 are arranged to sandwich thespiral electrode body 230 perpendicularly to a periphery surfacethereof.

A battery lid 224, and a safety valve mechanism 225 and a positivetemperature coefficient (PTC) element 226 which are positioned insidethe battery lid 224, are mounted in the open end of the battery can 221by caulking via a gasket 227 to seal the inside of the battery can 221.The battery lid 224 is made of the same material as that of the batterycan 221. The battery lid 224 is made of the same material as the batterycan 121. The safety valve mechanism 225 is electrically connected to thebattery lid 224 through a heat sensitive resistive element 226. When aninternal pressure of the battery becomes more than certain value due tointernal short circuit or heating from outside, a disk plate 225A isinverted to cut the electric connection between the battery lid 224 andthe spiral electrode body 230. The heat sensitive resistive element 226restricts electric currents, when its resistance increases with anincrease in temperature, to prevent unusual heat generation due to highelectric currents. The gasket 227 is made of an insulating material andasphalt is applied to the surface thereof.

The spiral electrode body 230 is wound around, for example, a center pin234. A cathode lead 235 containing aluminum Al or the like is connectedto the cathode 231 of the spiral electrode body 230, and an anode lead236 containing nickel Ni or the like is connected to the anode 232. Thecathode lead 235 is welded to the safety valve mechanism 225 to beelectrically connected with the battery lid 224. The anode lead 236 iswelded to the battery can 221 to be electrically connected.

FIG. 16 is a partly enlarged cross-sectional view showing the spiralelectrode body 230 shown in FIG. 15. The spiral electrode body 230 isformed by laminating and winding the cathode 231 and the anode 232 viathe separator 233.

For example, the cathode 231 has a cathode current collector 231A and acathode active material layer 231B that is formed on both sides of thecathode current collector 231A. For example, the anode 232 has an anodecurrent collector 232A and an anode active material layer 232B that isformed on both sides of the anode current collector 232A. Each structureof the cathode current collector 231A, the cathode active material layer231B, the anode current collector 232A, the anode active material layer232B, the separator 233, and the electrolytic solution is the same asthat of the cathode current collector 213A, the cathode active materiallayer 213B, the anode current collector 214A, the anode active materiallayer 214B, the separator 215, and the electrolytic solution in thefirst embodiment.

Subsequently, the method for manufacturing of the nonaqueous electrolytebattery of the third example will be described.

The cathode 231 is fabricated in the following manner. As describedabove, the cathode active material layer 231B is formed on the cathodecurrent collector 231A to obtain the cathode 231. Since the formationmethod of the positive active material layer 231B is the same asdescribed above, a detailed description will not be repeated here.

The anode 232 is fabricated in the following manner. First, the anodeactive material and the binder were mixed to prepare an anode mixtureand then the anode mixture was dispersed in a solvent such asN-methyl-2-pyrrolidone to give an anode mixture slurry. Next, the anodemixture slurry was applied to the anode current collector 232A and thesolvent was dried, followed by compression molding with a roll presserto form the anode active material layer 232B. Then, the anode 232 wasfabricated.

Next, the cathode lead 236 is fixed to the cathode current collector231A with welding or the like, and the anode lead 236 is fixed to theanode current collector 232A. Thereafter, the cathode 231 and the anode232 are wound sandwiching the separator 233 therebetween, a tip portionof the cathode lead 236 is welded to the safety valve mechanism 225, atip portion of the anode lead 236 is welded to the battery can 221, andthe wound cathode 231 and anode 232 are sandwiched between a pair of theinsulating plates 222 and 223, and then housed inside the battery can221. After housing the cathode 231 and anode 232 inside the battery can221, the electrolyte is injected into the battery can 221 to beimpregnated into the separator 233. Thereafter, the battery lid 224, thesafety valve mechanism 225, and the heat sensitive resistive element 226are caulked and fixed to an opening end of the battery can 221 throughthe gasket 227. As described above, the nonaqueous electrolyte batteryshown in FIG. 15 is fabricated.

Although a cylinder can is used as an exterior member in the thirdexample of the nonaqueous electrolyte battery, the generation of gas isinhibited by using the cathode produced by the method for manufacturinga cathode according to an embodiment. Therefore, breakage due to theincreased internal pressure that is produced by the generation of gascan be prevented.

Subsequently, the fourth example of the nonaqueous electrolyte batterywill be described. The fourth example is the nonaqueous electrolytebattery having a square shape. As shown in FIG. 17, in the fourthexample, a spiral electrode body 153 is housed in an exterior can 251having a square shape which is made of metals such as aluminium Al andiron Fe. Then, an electrode pin 254 provided on a battery lid 252 isconnected with an electrode terminal 255 drawn from the spiral electrodebody 153 and the exterior can is closed by the battery lid 252. Theelectrolytic solution is injected from an electrolytic solution inlet256, then the inlet is sealed by a sealing member 257 and the nonaqueouselectrolyte battery is fabricated. In this regard, the spiral electrodebody 153 is the same as the first example, a detailed description willnot be repeated here.

Although the exterior can 251 having a square shape can is used as anexterior member in the fourth example of the nonaqueous electrolytebattery, the generation of gas is inhibited by using the cathodeproduced by the method for manufacturing a cathode according to anembodiment. Therefore, breakage due to the increased internal pressurethat is produced by the generation of gas can be prevented.

Examples

Herein below, specific examples of the fifth embodiment will bedescribed, but the fifth embodiment is not to be construed as beinglimited thereto.

<Sample 1>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(0.98)Co_(0.20)Ni_(0.80)O_(2.1) and a mean particle diameter of 12 μmwhich was determined by the laser scattering method. While the resultingmixture was kneaded with N-methyl-2-pyrrolidone (NMP) and further 0.05parts by weight of phosphorous acid (H₃PO₃) was added thereto, which waswell kneaded for 1 hour. Thereafter, the obtained mixture was thinlyapplied onto Al foil 15 μm thick, which was dried, followed by cuttinginto the predetermined size and further vacuum drying at 100° C. orhigher, and thus the cathode electrode in Sample 1 was obtained.

<Sample 2>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(0.98)Co_(0.20)Ni_(0.80)O_(2.1) and a mean particle diameter of 12 μmwhich was determined by the laser scattering method. While the resultingmixture was kneaded with N-methyl-2-pyrrolidone (NMP) and further 0.10parts by weight of phosphorous acid (H₃PO₃) was added thereto, which waswell kneaded for 1 hour. Thereafter, the obtained mixture was thinlyapplied onto Al foil 15 μm thick, which was dried, followed by cuttinginto the predetermined size and further vacuum drying at 100° C. orhigher, and thus the cathode electrode in Sample 2 was obtained.

<Sample 3>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.05)O_(2.1) and a mean particle diameterof 14 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 0.20 parts by weight of phosphorous acid (H₃PO₃) was addedthereto, which was well kneaded for 1 hour. Thereafter, the obtainedmixture was thinly applied onto Al foil 15 μm thick, which was dried,followed by cutting into the predetermined size and thus the cathodeelectrode in Sample 3 was obtained.

<Sample 4>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.05)O_(2.1) and a mean particle diameterof 14 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 0.50 parts by weight of H₃PO₃ was added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil 15 μm thick, which was dried, followed by cutting into thepredetermined size and thus the cathode electrode in Sample 4 wasobtained.

<Sample 5>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.05)O_(2.1) and a mean particle diameterof 14 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 1.0 parts by weight of H₃PO₃ was added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil 15 μm thick, which was dried, followed by cutting into thepredetermined size and thus the cathode electrode in Sample 4 wasobtained.

<Sample 6>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.05)O_(2.1) and a mean particle diameterof 14 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 3.0 parts by weight of H₃PO₃ was added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil 15 μm thick, which was dried, followed by cutting into thepredetermined size and thus the cathode electrode in Sample 6 wasobtained.

<Sample 7>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.05)O_(2.1) and a mean particle diameterof 14 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 5.0 parts by weight of H₃PO₃ was added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil 15 μm thick, which was dried, followed by cutting into thepredetermined size and thus the cathode electrode in Sample 7 wasobtained.

<Sample 8>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(1.02)Co_(0.98)Mg_(0.01)Al_(0.01)O_(2.1) and a mean particle diameterof 12 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 0.01 parts by weight of H₃PO₃ was added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil 15 μm thick, which was dried, followed by cutting into thepredetermined size and further vacuum drying at 100° C. or higher, andthus the cathode electrode in Sample 8 was obtained.

<Sample 9>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(1.02)Co_(0.98)Mg_(0.01)Al_(0.01)O_(2.1) and a mean particle diameterof 12 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 0.10 parts by weight of H₃PO₃ was added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil 15 μm thick, which was dried, followed by cutting into thepredetermined size and further vacuum drying at 100° C. or higher, andthus the cathode electrode in Sample 9 was obtained.

<Sample 10>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(1.02)Co_(0.98)Mg_(0.01)Al_(0.01)O_(2.1) and a mean particle diameterof 12 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 0.50 parts by weight of H₃PO₃ was added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil 15 μm thick, which was dried, followed by cutting into thepredetermined size and further vacuum drying at 100° C. or higher, andthus the cathode electrode in Sample 10 was obtained.

<Sample 11>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(1.02)Co_(0.98)Mg_(0.01)Al_(0.01)O_(2.1) and a mean particle diameterof 12 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 1.0 parts by weight of H₃PO₃ was added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil 15 μm thick, which was dried, followed by cutting into thepredetermined size and further vacuum drying at 100° C. or higher, andthus the cathode electrode in Sample 11 was obtained.

<Sample 12>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.05)O_(2.1) and a mean particle diameterof 14 μm which was determined by the laser scattering method. Theresulting mixture was well kneaded with N-methyl-2-pyrrolidone (NMP) for1 hour. Thereafter, the obtained mixture was thinly applied onto Al foil15 μm thick, which was dried and then cut into the predetermined size,and the cathode electrode in Comparison 7 was obtained.

<Sample 13>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of compositehydroxide particles having an average composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.05)O_(2.1) and a mean particle diameterof 14 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 0.005 parts by weight of H₃PO₃ was added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil 15 μm thick, which was dried and then cut into thepredetermined size, and the cathode electrode in Comparison 2 wasobtained.

<Sample 14>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of compositehydroxide particles having an average composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.05)O_(2.1) and a mean particle diameterof 14 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP), 7.0parts by weight of H₃PO₃ was further added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil 15 μm thick, which was dried and then cut into thepredetermined size, and the cathode electrode in Example 14 wasobtained.

<Sample 15>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of compositehydroxide particles having an average composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.05)O_(2.1) and a mean particle diameterof 14 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 3.0 parts by weight of H₃PO₃ was added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thickly appliedonto Al foil 15 μm thick, which was dried and then cut into thepredetermined size, and the cathode electrode in Example 15 wasobtained.

<Sample 16>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of compositehydroxide particles having an average composition ofLi_(0.98)Co_(0.15)Ni_(0.80)Al_(0.05)O_(2.1) and a mean particle diameterof 14 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 5.0 parts by weight of H₃PO₃ was added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thickly appliedonto Al foil 15 μm thick, which was dried and then cut into thepredetermined size, and the cathode electrode in Example 16 wasobtained.

<Sample 17>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(1.02)Co_(0.98)Mg_(0.01)Al_(0.01)O_(2.1) and a mean particle diameterof 12 μm which was determined by the laser scattering method. Theresulting mixture was well kneaded with N-methyl-2-pyrrolidone (NMP) for1 hour. Thereafter, the obtained mixture was thinly applied onto Al foil15 μm thick, which was dried and then cut into the predetermined size,and the cathode electrode in Sample 17 was obtained.

<Sample 18>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(1.02)Co_(0.98)Mg_(0.01)Al_(0.01)O_(2.1) and a mean particle diameterof 12 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 0.005 parts by weight of H₃PO₃ was added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil 15 μm thick, which was dried and then cut into thepredetermined size, and the cathode electrode in Sample 18 was obtained.

<Sample 19>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1.0 parts byweight of graphite were added to 100 parts by weight of compositehydroxide particles having an average composition ofLi_(1.02)Co_(0.98)Mg_(0.01)Al_(0.01)O_(2.1) and a mean particle diameterof 12 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 0.008 parts by weight of H₃PO₃ was added thereto, which was wellkneaded for 1 hour. Thereafter, the obtained mixture was thinly appliedonto Al foil 15 μm thick, which was dried and then cut into thepredetermined size, and the cathode electrode in Sample 19 was obtained.

<Sample 20>

2.0 parts by weight of polyvinylidene fluoride (PVdF) and 1 parts byweight of graphite were added to 100 parts by weight of composite oxideparticles having an average composition ofLi_(1.02)Co_(0.98)Mg_(0.01)Al_(0.01)O_(2.1) and a mean particle diameterof 12 μm which was determined by the laser scattering method. While theresulting mixture was kneaded with N-methyl-2-pyrrolidone (NMP) andfurther 6.0 parts by weight of phosphorous acid (H₃PO₃) was addedthereto, which was well kneaded for 1 hour. Thereafter, the obtainedmixture was thinly applied onto Al foil 15 μm thick, which was dried,followed by cutting into the predetermined size, and thus the cathodeelectrode in Sample 20 was obtained.

As for the produced cathode electrodes of Samples 1 to 20, the bendingtest was performed in order to examine the winding characteristics ofthe electrode in the case where the amount and type of additive agent ischanged. The bending test was performed in the following manner. Afterdrying, the cathode active materials of the cathode electrodes ofSamples 1 to 20 were pressed so as to be a predetermined volume density.Further, the cathode electrodes after pressing were subjected to vacuumdrying. Thereafter, the cathode electrodes were bent in half and theoccurrence of breakage, cracking, or cutting of the coated foil wasvisually confirmed. Test results are shown in Table 3. In Table 3, theevaluation of breaking or cracking of a cathode electrode is indicatedby a “∘” mark or a “×” mark.

TABLE 3 COMPOSITION OF CATHODE WINDING CHARACTERISTICS ACTIVE MATERIALADDITION VOLUME DENSITY [g/cm³] (MOLAR RATIO) AMOUNT (THICKNESS OFELECTRODE [μm) Ni Co Al ADDITIVE [wt %] 3.20-3.25 3.30-3.35 3.40-3.45SAMPLE 1 80 20 0 H₃PO₃ 0.05 ∘ (155 μm) ∘ (151 μm) ∘ (146 μm) SAMPLE 2 8020 0 H₃PO₃ 0.10 ∘ (192 μm) ∘ (186 μm) ∘ (181 μm) SAMPLE 3 80 15 5 H₃PO₃0.20 ∘ (155 μm) ∘ (150 μm) ∘ (145 μm) ∘ (192 μm) ∘ (186 μm) ∘ (181 μm)SAMPLE 4 80 15 5 H₃PO₃ 0.50 ∘ (192 μm) ∘ (186 μm) ∘ (181 μm) ∘ (213 μm)∘ (207 μm) ∘ (202 μm) SAMPLE 5 80 15 5 H₃PO₃ 1.0 ∘ (155 μm) ∘ (151 μm) ∘(146 μm) ∘ (213 μm) ∘ (207 μm) ∘ (202 μm) SAMPLE 6 80 15 5 H₃PO₃ 3.0 ∘(210 μm) ∘ (204 μm) ∘ (199 μm) ∘ (234 μm) ∘ (228 μm) ∘ (222 μm) SAMPLE 780 15 5 H₃PO₃ 5.0 ∘ (210 μm) ∘ (204 μm) ∘ (199 μm) ∘ (234 μm) ∘ (228 μm)∘ (222 μm) SAMPLE 8 98 1 1 H₃PO₃ 0.01 ∘ (139 μm) ∘ (135 μm) ∘ (132 μm)SAMPLE 9 98 1 1 H₃PO₃ 0.10 ∘ (153 μm) ∘ (149 μm) ∘ (145 μm) ∘ (170 μm) ∘(165 μm) ∘ (161 μm) SAMPLE 10 98 1 1 H₃PO₃ 0.50 ∘ (153 μm) ∘ (149 μm) ∘(145 μm) ∘ (170 μm) ∘ (165 μm) ∘ (161 μm) SAMPLE 11 98 1 1 H₃PO₃ 1.0 ∘(170 μm) ∘ (165 μm) ∘ (161 μm) ∘ (213 μm) ∘ (207 μm) ∘ (202 μm) SAMPLE12 80 15 5 — — ∘ (155 μm) x (150 μm) x (145 μm) SAMPLE 13 80 15 5 H₃PO₃0.005 ∘ (155 μm) x (150 μm) x (145 μm) SAMPLE 14 80 15 5 H₃PO₃ 7.0DIFFICULTY IN PRESSING DUE TO PEELING-OFF OF ACTIVE MATERIAL SAMPLE 1580 15 5 H₃PO₃ 3.0 ∘ (256 μm) x (248 μm) x (242 μm) SAMPLE 16 80 15 5H₃PO₃ 5.0 ∘ (256 μm) ∘ (248 μm) x (242 μm) SAMPLE 17 98 1 1 — — ∘ (153μm) x (149 μm) x (145 μm) SAMPLE 18 98 1 1 H₃PO₃ 0.005 ∘ (153 μm) x (149μm) x (145 μm) SAMPLE 19 98 1 1 H₃PO₃ 0.008 ∘ (170 μm) x (165 μm) x (161μm) SAMPLE 20 98 1 1 H₃PO₃ 6.0 DIFFICULTY IN PRESSING DUE TO PEELING-OFFOF ACTIVE MATERIAL *∘: CUTTING OR CRACKING OF ELECTRODES ARE NOTOBSERVED x: CUTTING OR CRACKING OF ELECTRODES ARE OBSERVED

As shown in Table 3, in the cathodes of Samples 1 to 11, cutting orcracking of the electrodes was not occurred even when the volume densityis in a range of 3.30 g/cm³ to 3.35 g/cm³ or in a range of 3.40 g/cm³ to3.45 g/cm³. On the other hand, cutting or cracking of the electrodes wasoccurred in Samples 12, 13, 15, 17, 18, and 19. In the cathode of Sample16, when the volume density is in a range of 3.40 g/cm³ to 3.45 g/cm³,cutting or cracking of the electrode was occurred. In the case ofSamples 14 and 20, the active material could not be pressed due to itspeeling.

A laminated cell (a size of 542436 and a rating of 1000 mAh) wasfabricated by using the cathode electrodes of Samples 1 to 11 andlaminating an outer face with aluminum. In this regard, the usedelectrolytic solution had a composition in which LiPF was dissolved in amixed solvent prepared by mixing ethylene carbonate (EC) and diethylcarbonate (DEC) at a weight ratio of EC:DEC=3:7 so as to be LiPF₆1mol/kg and further 5 parts by weight of vinylene carbonate (VC) wasadded thereto.

Next, the laminated cell thus fabricated was subjected to the followingcharge and discharge test and then the capacity maintenance rate after500 cycles was determined

(Charge and Discharge Test)

The capacity maintenance rate was determined by the ratio of thedischarge capacity of the 500th cycle at 23° C. to the dischargecapacity of the 1st cycle at 23° C., namely, (“discharge capacity of the500th cycle at 23° C.”/“discharge capacity of the 1st cycle at 23°C.”)×100. In this regard, the charging was performed at a constantcurrent of 1 C under a constant voltage condition (up to the upper limitvoltage of 4.2 V) and the discharging was performed at a constantcurrent of 1 C (up to the final voltage of 2.5 V).

The measured results are shown in Table 4.

TABLE 4 CAPACITY MAINTENANCE VOLUME DENSITY [g/cm³] RATE (CAPACITY OFTHE ADDITION (THICKNESS OF 500TH CYCLE/ AMOUNT ELECTRODE) CAPACITY OFTHE 1ST ADDITIVE [wt %] 3.40-3.45 CYCLE) [%] SAMPLE 1 H₃PO₃ 0.05 ∘ (146μm) 74.0 SAMPLE 2 H₃PO₃ 0.10 ∘ (181 μm) 72.4 SAMPLE 3 H₃PO₃ 0.20 ∘ (145μm) 74.2 ∘ (181 μm) 72.7 SAMPLE 4 H₃PO₃ 0.50 ∘ (181 μm) 72.0 ∘ (202 μm)71.2 SAMPLE 5 H₃PO₃ 1.0 ∘ (146 μm) 73.1 SAMPLE 6 H₃PO₃ 3.0 ∘ (199 μm)71.1 ∘ (222 μm) 70.0 SAMPLE 7 H₃PO₃ 5.0 ∘ (199 μm) 70.5 ∘ (222 μm) 70.1SAMPLE 8 H₃PO₃ 0.01 ∘ (132 μm) 82.1 SAMPLE 9 H₃PO₃ 0.10 ∘ (145 μm) 76.1∘ (161 μm) 75.5 SAMPLE 10 H₃PO₃ 0.50 ∘ (145 μm) 76.3 ∘ (161 μm) 75.2SAMPLE 11 H₃PO₃ 1.0 ∘ (161 μm) 75.0 ∘ (202 μm) 73.7 *∘: CUTTING ORCRACKING OF ELECTRODES ARE NOT OBSERVED

As shown in Table 4, in the laminated cell formed by using cathodes ofSamples 1 to 7, sufficient cycle characteristics were obtained. That is,it was confirmed that, when the lithium composite oxide containinghigher proportion of nickel Ni than that of cobalt Co was used,sufficient cycle characteristics were obtained by adding phosphorousacid (H₃PO₃) in a range of 0.05 parts by weight to 5.0 parts by weightto 100 parts by weight of cathode active material. In the laminated cellformed by using cathodes of Samples 8 to 11, sufficient cyclecharacteristics were obtained. That is, it was confirmed that, when thelithium composite oxide containing lower proportion of nickel Ni thanthat of cobalt Co was used, sufficient cycle characteristics wereobtained by adding phosphorous acid (H₃PO₃) in a range of 0.01 parts byweight to 1.0 parts by weight to 100 parts by weight of cathode activematerial.

Further, the cathode electrode was observed with an electron microscope.Electron micrographs of the surface of the cathode electrode in Samples2 and 12 are shown in FIGS. 18A and 18B.

FIG. 18A is an electron micrograph of the surface of the cathodeelectrode in Sample 2. FIG. 18B is an electron micrograph of the surfaceof the cathode electrode in Sample 12. On the surface of Sample 12, thebinder and the conductive auxiliary agent (black colored area) areincorporated into a gap between the primary particles of the cathodeactive material (gray area) and a net shape is formed. On the otherhand, in Sample 1, the binder and the conductive auxiliary agent arehardly incorporated into a gap between the primary particles. It isconsidered that lower amounts of the binder and the conductive auxiliaryagent between primary particles allow lithium ions to move easily.

Further, the electrode surface of Samples 2 and 12 was determined byTOF-SIMS. The results of the cathode electrode in Samples 2 and 12 whichare determined based on TOF-SIMS positive secondary ion massspectrometry are shown in FIGS. 19A and 19B as well as FIGS. 20A and20B. The results of the cathode electrode in Samples 2 and 12, which aredetermined based on TOF-SIMS negative secondary ion mass spectrometry,are shown in FIG. 21.

As shown in FIGS. 19 to 21, a peak of a fragment based on positivesecondary ions of C₃F₅, C₅F₉, C₇F₁₃, and Li₄PO₄ and negative secondaryions of PO₂, PO₃, LiP₂O₄, LiP₂O₅, LiP₂O₆, LiPO₂F, LiPO₃F, POF₂, PO₂F₂,and LiPO₃H was observed.

Further, the results of the surface analysis by X-ray photoelectronspectroscopy in Samples 2 and 12 are shown in FIG. 22. The line a showsthe analysis results of the cathode electrode before charging anddischarging of Sample 2. The line b shows the analysis results of thecathode electrode after the first charging and discharging of Sample 2.The line c shows the analysis results of the cathode electrode after thefirst charging and discharging of Sample 12. Here, the cathode electrodeafter the first charging and discharging is the cathode electrode whichis washed with dimethyl carbonate (DMC) after dismounting of thebattery, followed by vacuum drying at 50° C.

As shown in FIG. 22, the P 2p spectrum derived from LiPF6 in theelectrolytic solution used for the battery was also observed after thefirst charging and discharging in Sample 12, where phosphorous acid(H₃PO₃) was not added. The difference between Sample 12 and Sample 2 isclear from the difference of the peak intensity and a peak in the P 2pspectrum derived from the phosphorus compound contained in the cathodecan be confirmed.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof. Forexample, the cathode active material layer 13B may contain other cathodeactive materials in addition to the cathode active materials describedabove. Examples of other cathode active materials include a lithiummanganese composite oxide having a spinel structure that containslithium and manganese Mn.

In addition, as the batteries formed by using the cathode produced bythe manufacture method according to an embodiment, the so-calledlithium-ion secondary battery in which the capacity of the anode isrepresented by a capacity component determined by occlusion and releaseof lithium has been described in the above-mentioned embodiments andExamples. The present application can be similarly applied to theso-called lithium metal secondary battery in which lithium metal is usedfor the anode active material and the capacity of the anode isrepresented by a capacity component determined by precipitation anddissolution of lithium. Further, the present application can besimilarly applied to the secondary battery in which the capacity of theanode is represented by the sum of the capacity component determined byocclusion and release of lithium and the capacity component determinedby precipitation and dissolution of lithium by lowering the chargingcapacity of the anode material capable of occluding and releasinglithium than the charging of the cathode.

Furthermore, as the batteries formed by using the cathode produced bythe manufacture method according to an embodiment, the secondarybatteries a flat type, a cylindrical type, and a square type have beendescribed in the above-mentioned embodiments and Examples. The presentapplication can be similarly applied to the secondary batteries of abutton type, a thin type, a large type, and a stacked lamination type.The present application can be applied to not only the secondarybatteries but also the primary batteries.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

The invention is claimed as follows:
 1. A cathode active materialmixture comprising: a lithium composite oxide which contains the highestproportion of nickel among constituent metal elements except lithium;and a phosphorus compound which is contained near a surface of thelithium composite oxide, wherein a peak of a fragment of at least onesecondary ion selected from the group consisting of positive secondaryions of Li₄PO₄, C₃F₅, C₅F₉, C₇F₁₃, negative secondary ions of PO₂, PO₃,LiP₂O₄, LiP₂O₅, LiP₂O₆, LiPO₂F, LiPO₃F, POF₂, PO₂F₂, and LiPO₃H based ona surface analysis by TOF-SIMS is observed near the surface, and whereina concentration of carbonate and bicarbonate in the cathode activematerial is greater than 0 and not more than 0.30% by weight.
 2. Thecathode active material according to claim 1, wherein the lithiumcomposite oxide, has an average composition represented by Formula 1:Li_(x)Co_(y)Ni_(z)M_(1-y-z)O_(b-a)X_(a)  (Chemical formula 1) wherein Mis one or more elements selected from the group consisting of boron B,magnesium Mg, aluminum Al, silicon Si, phosphorus P, sulfur S, titaniumTi, chromium Cr, manganese Mn, iron Fe, copper Cu, zinc Zn, gallium Ga,germanium Ge, yttrium Y, zirconium Zr, molybdenum Mo, silver Ag, bariumBa, tungsten W, indium In, tin Sn, lead Pb, and antimony Sb; X ishalogen; and x, y, z, a, and b are values in the range of 0.8<x≦1.2,0≦y≦0.5, 0.5≦z≦1.0, 1.8≦b≦2.2, and 0≦a≦1.0, respectively.
 3. The cathodeactive material according to claim 2, wherein 0.6≦z≦1.0.
 4. The cathodeactive material according to claim 1, wherein the phosphorus compound isa compound in which the binding energy peak in the P 2p spectrum basedon X-ray photoelectron spectroscopy is in the range of 132 to 135 eV. 5.The cathode active material according to claim 1, wherein at least apart of the phosphorus compound is represented by Formula 2:Li_(c)H_(d)P_(e)O_(f)  (Chemical formula 2) wherein c, e, and frepresent an integer of 1 or more; and d represents an integer of 0 ormore.
 6. The cathode active material according to claim 1, wherein atleast a part of the phosphorus compound is represented by Formula 3:Li_(g)PO_(h)F_(i)  (Chemical formula 3) wherein g, h, and i represent aninteger of 1 or more.
 7. The cathode active material according to claim1, wherein the cathode active material has a peak of a fragment of atleast one secondary ion selected from the group consisting of a positivesecondary ion of Li₄PO₄, negative secondary ions of PO₂, PO₃, LiP₂O₄,LiP₂O₅, and LiP₂O₆ based on the surface analysis by TOF-SIMS.
 8. Thecathode active material according to claim 1, wherein a concentration ofcarbonate and bicarbonate in the cathode active material is not morethan 0.21% by weight.
 9. The cathode active material according to claim1, wherein a molar ratio of manganese in the lithium composite oxide isless than or equal to 0.05.
 10. The cathode active material according toclaim 1, wherein the lithium composite oxide has an average compositionselected from the group consisting of:Li_(0.98)Co_(0.20)Ni_(0.77)Al_(0.03)O_(2.1),Li_(0.98)Co_(0.15)Ni_(0.80)Al_(0.05)O_(2.1),Li_(0.98)Co_(0.15)Ni_(0.80)Mn_(0.05)O_(2.1),Li_(0.98)Co_(0.15)Ni_(0.80)Al_(0.04)Ba_(0.01)O_(2.1),Li_(0.98)Co_(0.15)Ni_(0.80)Al_(0.04)Sn_(0.01)O_(2.1),Li_(0.98)Co_(0.20)Ni_(0.80)O_(2.1),Li_(0.98)Co_(0.28)Ni_(0.70)Al_(0.02)O_(2.1) andLi_(0.98)Co_(0.40)Ni_(0.60)O_(2.1).
 11. A cathode comprising: a cathodeactive material mixture having a lithium composite oxide which containsthe highest proportion of nickel among constituent metal elements exceptlithium; and a phosphorus compound which is contained near a surface ofthe lithium composite oxide, wherein the cathode has a peak of afragment of at least one secondary ion selected from the groupconsisting of positive secondary ions of Li₄PO₄, C₃F₅, C₅F₉, C₇F₁₃,negative secondary ions of PO₂, PO₃, LiP₂O₄, LiP₂O₅, LiP₂O₆, LiPO₂F,LiPO₃F, POF₂, PO₂F₂, and LiPO₃H based on a surface analysis by TOF-SIMSis observed near the surface, and wherein a concentration of carbonateand bicarbonate in the cathode active material is greater than 0 and notmore than 0.30% by weight.
 12. The cathode according to claim 11,wherein the lithium composite oxide is represented by Formula 1:Li_(x)Co_(y)Ni_(z)M_(1-y-z)O_(b-a)X_(a)  (Chemical formula 1) wherein Mis one or more elements selected from the group consisting of boron B,magnesium Mg, aluminium Al, silicon Si, phosphorus P, sulfur S, titaniumTi, chromium Cr, manganese Mn, iron Fe, copper Cu, zinc Zn, gallium Ga,germanium Ge, yttrium Y, zirconium Zr, molybdenum Mo, silver Ag, bariumBa, tungsten W, indium In, tin Sn, lead Pb, and antimony Sb; X ishalogen; and x, y, z, a, and b are values in the range of 0.8<x≦1.2,0≦y≦0.5, 0.5≦z≦1.0, 1.8≦b≦2.2, and 0≦a≦1.0, respectively.
 13. Thecathode according to claim 11, wherein the phosphorus compound is acompound in which the binding energy peak in the P 2p spectrum based onX-ray photoelectron spectroscopy is in the range of 132 to 135 eV. 14.The cathode according to claim 11, wherein at least a part of thephosphorus compound is represented by Formula 2:Li_(c)H_(d)P_(e)O_(f)  (Chemical formula 2) wherein c, e, and frepresent an integer of 1 or more; and d represents an integer of 0 ormore.
 15. The cathode according to claim 11, wherein at least a part ofthe phosphorus compound is represented by Formula 3:Li_(g)PO_(h)F_(i)  (Chemical formula 3) wherein g, h, and i represent aninteger of 1 or more.
 16. The cathode according to claim 11, wherein aconcentration of carbonate and bicarbonate in the cathode activematerial is not more than 0.21% by weight.
 17. A nonaqueous electrolytebattery comprising: a cathode, an anode, and an electrolyte, wherein thecathode includes a cathode active material mixture including a lithiumcomposite oxide which contains the highest proportion of nickel iscontained among constituent metal elements except lithium and aphosphorus compound near a surface of the lithium composite oxide,wherein the cathode has a peak of a fragment of at least one secondaryion selected from the group consisting of positive secondary ions ofLi₄PO₄, C₃F₅, C₅F₉, C₇F₁₃, negative secondary ions of PO₂, PO₃, LiP₂O₄,LiP₂O₅, LiP₂O₆, LiPO₂F, LiPO₃F, POF₂, PO₂F₂, and LiPO₃H based on asurface analysis by TOF-SIMS is observed near the surface, and wherein aconcentration of carbonate and bicarbonate in the cathode activematerial is greater than 0 and not more than 0.30% by weight.
 18. Thenonaqueous electrolyte battery according to claim 17, wherein thelithium composite oxide, has an average composition represented byFormula 1:Li_(x)Co_(y)Ni_(z)M_(1-y-z)O_(b-a)X_(a)  (Chemical formula 1) wherein Mis one or more elements selected from the group consisting of boron B,magnesium Mg, aluminium Al, silicon Si, phosphorus P, sulfur S, titaniumTi, chromium Cr, manganese Mn, iron Fe, copper Cu, zinc Zn, gallium Ga,germanium Ge, yttrium Y, zirconium Zr, molybdenum Mo, silver Ag, bariumBa, tungsten W, indium In, tin Sn, lead Pb, and antimony Sb; X ishalogen; and x, y, z, a, and b are values in the range of 0.8<x≦1.2,0≦y≦0.5, 0.5≦z≦1.0, 1.8≦b≦2.2, and 0≦a≦1.0, respectively.
 19. Thenonaqueous electrolyte battery according to claim 17, wherein thephosphorus compound is a compound in which the binding energy peak inthe P 2p spectrum based on X-ray photoelectron spectroscopy is in therange of 132 to 135 eV.
 20. The nonaqueous electrolyte battery accordingto claim 17, wherein at least a part of the phosphorus compound isrepresented by Formula 2:Li_(c)H_(d)P_(e)O_(f)  (Chemical formula 2) wherein c, e, and frepresent an integer of 1 or more; and d represents an integer of 0 ormore.
 21. The nonaqueous electrolyte battery according to claim 17,wherein at least a part of the phosphorus compound is represented byFormula 3:Li_(g)PO_(h)F_(i)  (Chemical formula 3) wherein g, h, and i represent aninteger of 1 or more.
 22. The nonaqueous electrolyte battery accordingto claim 17, wherein a concentration of carbonate and bicarbonate in thecathode active material is not more than 0.21% by weight.
 23. Thenonaqueous electrolyte battery according to claim 17, comprising acylindrical can, a square-type can, or a laminate film as an exteriormember.
 24. The nonaqueous electrolyte battery according to claim 17,wherein the nonaqueous electrolyte battery includes a spiral electrodebody formed by winding the cathode and the anode and has a flat orsquare shape.